Parabolic Troughs
www.ParabolicTroughs.net

We provide Parabolic Trough Collectors, Concentrating Solar Power systems and other turnkey solar power and energy solutions, from project design and engineering, to financing permitting and installation.  This includes Solar Water Heating Systems, Solar Electric Power Systems, Solar CHP, Solar Cogeneration and Solar Trigeneration power and energy systems.  We also offer energy-saving technologies that may include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Cogeneration, Demand Response Programs, Demand Side Management, Energy Master Planning, Engine Driven Chillers, Trigeneration and Energy Conservation Measures.  

Solar Energy Systems is a subsidiary of Cogeneration Technologies. We provide the following power and energy project development services: 

• Project Engineering Feasibility & Economic Analysis Studies  

• Engineering, Procurement and Construction

• Environmental Engineering & Permitting 

• Project Funding & Financing Options; including Equity Investment, Debt Financing, Lease and Municipal Lease

• Shared/Guaranteed Savings Program with No Capital Investment from Qualified Clients 

• Project Commissioning 

• 3rd Party Ownership and Project Development

• Long-term Service Agreements

• Operations & Maintenance 

• Green Tag (Renewable Energy Credit, Carbon Dioxide Credits, Emission Reduction Credits) Brokerage Services; Application and Permitting

We provide Net Energy Metering project development services as well as "turnkey" products and services in the areas of "Renewable Energy Technologies" and in developing clean power/energy projects that will generate a "Renewable Energy Credit," Carbon Dioxide Credits  and Emission Reduction Credits.  Through our strategic partners, we offer "turnkey" power/energy project development products and services that may include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Biodiesel Refineries, Biofuel Refineries, Biomass Gasification, BioMethane, Canola Biodiesel, Coconut Biodiesel, Cogeneration, Concentrating Solar Power, Demand Response Programs, Demand Side Management, Energy Conservation Measures, Energy Master Planning, Engine Driven Chillers, Solar CHP, Solar Cogeneration, Rapeseed Biodiesel, Solar Electric Heat Pumps, Solar Electric Power Systems, Solar Heating and Cooling, Solar Trigeneration, Soy Biodiesel, and Trigeneration.

Unlike most companies, we are equipment supplier/vendor neutral. This means we help our clients select the best equipment for their specific application. This approach provides our customers with superior performance, decreased operating expenses and increased return on investment. 

For more information: call us at: 832-758-0027

What are Parabolic Trough Collectors?

The parabolic trough is the most advanced of the concentrator systems.  This technology is used in the largest grid connected solar-thermal power plants in the world.  One such complex in the U.S. uses parabolic troughs.  The Kramer Junction companies operate and maintain five 30-megawatt Solar Electric Generating Systems (SEGS). These SEGS comprise 150 to 354 megawatts of installed parabolic trough solar thermal electric generating capacity located in California's Mojave desert. The combined California facilities produce more than 99% of the commercially available solar generated electric power in the U.S.

A parabolic trough collector has a linear parabolic-shaped reflector that focuses the sun's radiation on a linear receiver located at the focus of the parabola.  The collector tracks the sun along one axis from east to west during the day to ensure that the sun is continuously focused on the receiver.  Because of its parabolic shape, a trough can focus the sun at 30 to 100 times its normal intensity (concentration ratio) on a receiver pipe located along the focal line of the trough, achieving operating temperatures over 400 degrees Celcius.

A collector field consists of a large field of single-axis tracking parabolic trough collectors.  The solar field is modular in nature and is composed of many parallel rows of solar collectors aligned on a north-south horizontal axis.  A working (heat transfer) fluid is heated as it circulates through the receivers and returns to a series of heat exchangers at a central location where the fluid is used to generate high-pressure superheated steam.  The steam is then fed to a conventional steam turbine/generator to produce electricity.  After the working fluid passes through the heat exchangers, the cooled fluid is recirculated through the solar field.  The plant is usually designed to operate at full rated power using solar energy alone, given sufficient solar energy.   However, all plants are hybrid solar/fossil plants that have a fossil-fired capability that can be used to supplement the solar output during periods of low solar energy.  The Luz plant is a natural gas hybrid.

What are Flat Plate Collectors?

Flat Plate Collectors are the most common type of solar water heating systems for residential and commercial applications.  Flat plate collectors are similar to a car's radiator, except that instead of moving heat away from a car's engine, through the airstream of the car's radiator, a flat plate collector collects the solar energy of the sun and transfers it to the home.  A flat plate collector is made up of one or more  dark metal plates, that are covered with a sheet of glass, which absorbs the solar energy of the sun and converts that solar energy into heat, in the form of hot water. The solar heat can be transferred either air or water (or other fluids in more sophisticated flat plate collector systems).  Flat plate collector systems are used comfort heating of a home or commercial building in the winter and for domestic hot water production throughout the year. Flat plate collectors usually heat water to temperatures ranging from 150° to 200° F (66° to 93° C). The efficiency of flat plate collectors varies from manufacturer to manufacturer, and system to system, but usually ranges from as low as 20% to as high as 80%.

What is Direct Solar Steam?

Direct Solar Steam is also referred to as "Direct Steam Generation." For a number of years it has been proposed that parabolic-trough systems will benefit in both performance and cost from generation of steam directly in the solar field, eliminating the expensive heat transfer fluid, the thermodynamic disadvantages of an intermediate heat transport system between the solar field and power block, and the HTF-to-steam heat exchangers. Although there are both pros and cons to this approach, it has generally been viewed positively by LUZ and the current trough development community. An important prototype development is currently under way at several location with one to two rows of collectors. Because some flow-instability studies have suggested that instabilities between a higher number of parallel rows may be the most important concern, further prototype systems may be required after testing at the PSA.

In recent years, trough technology has sometimes been viewed as dated, with limited potential for continued reduction in the levelized cost of electricity; however, trough workshop participants identified a number of opportunities that will likely lead to substantial cost reduction and performance improvement over the current trough technology.

• Power Plant Size
  Increasing plant size is one of the easiest ways to reduce the cost of solar electricity from parabolic-trough power plants. Studies have shown that doubling the size reduces the capital cost by approximately 12%–14%. This cost reduction typically comes from several factors. Economies of scale due to increased manufacturing volume reduce unit costs for both the power block and solar field. Also, O&M costs for larger plants will typically be less on a per-kilowatt basis because significantly fewer operators and somewhat fewer maintenance crews per megawatt are needed for larger plants. Power plant maintenance costs will be reduced with larger plants, but solar field maintenance costs, while lower, will scale more linearly with solar field size.

• ISCCS
  The Integrated Solar Combined-Cycle System is a proposed configuration that would utilize the steam bottoming cycle in a combined cycle plant to convert the solar thermal energy into electricity. In the ISCCS configuration, the steam turbine would be increased in size by as much as 100% over the conventional combined cycle. The ISCCS design offers a number of potential advantages over a stand-alone Rankine-cycle plant. The incremental capital and O&M costs of the ISCCS are significantly lower than the cost of a conventional Rankine plant. Also, the solar electric operating efficiency should be higher due to reduced start-up losses. However, some design optimization remains to be completed to minimize the potential impact to gas-mode operation. Initial studies show that the ISCCS configuration could reduce the cost of solar power by as much as 22% over the blended cost of power from a conventional SEGS plant (25% fossil) of similar size.

• Advanced Trough Collector
  As illustrated above, the structure constitutes about 40% of the solar field cost, whereas the reflectors and receivers each cost from 20%–25% of the total. In the SEGS design, steel provides the major strength, with thick glass mirror panels giving the parabolic shape to the reflecting surface. Lower-cost designs can be explored for the steel structure, with a possible alternative of a lighter aluminum or composite structure integrated with a front surface reflector on film, thin glass, or structural member. Evolutionary improvements in the receivers are also possible.

• Direct Steam Generation (DSG)
  In the DSG concept, steam is generated directly in the parabolic-trough collectors. This saves cost by eliminating the need for the heat transfer fluid (HTF) system and reduces the efficiency loss involved with using a heat exchanger to generate steam. DSG should also improve the solar field operating efficiency due to lower average operating temperatures and improved heat transfer in the collector receiver. The trough collectors would require some modification due to the higher operating pressure and lower fluid flow rates. Control of a DSG solar field likely will be more complicated than the HTF systems and may require a more complex design layout and tilted collector. DSG also makes it more difficult to provide any thermal storage. A pilot demonstration of DSG technology is in progress at the Plataforma Solar de Almer�(PSA) in Spain.

• Solar Power Park Development
  One opportunity for significantly reducing the cost of CSP plants is to develop multiple plants at the same location in a solar power park environment. The power park offers a number of potential opportunities for reducing cost. If multiple projects are planned together, project development and engineering costs per project will likely be reduced. If the O&M is performed by a single company, significant reductions in overhead and improved O&M efficiency and skill coverage are possible. If the plants are built consecutively and the same construction crews are used for all plants, construction costs should be reduced through labor learning curve efficiencies. Multiple projects will mean multi-year manufacturing runs on solar collector components, resulting in reduced cost per collector. Competitive bidding of major power plant equipment, materials, and services will likely result in greater cost reduction for multiple projects. Building five plants in a phased project approach at the same site could in fact reduce costs by 25%–30% for a single project.

• Project Financial Structure
  Parabolic-trough plants are capital-intensive projects. The cost of capital and the type of project financing can have a significant impact on the final cost of power. In the past, the SEGS projects were all financed as IPP projects. Significant cost reductions are possible if projects are owned by investor-owned utilities (IOUs), municipal utilities, or by the new generation companies (GenCos) that are being created as part of utility restructuring. Cost reductions approximately 10%–40% are possible through alternative ownership and financing structures.

• Tax Equity
  Studies have shown that capital-intensive power projects, such as parabolic-trough plants, pay a higher percentage of taxes than expense-intensive projects, such as fossil fuel technologies. One study for the California Energy Commission comparing taxes paid by concentrating solar power technologies with taxes paid by fossil technologies showed that approximate tax equity was achieved with a 20% federal investment tax credit and property tax exemption for CSP technologies. Tax equity in this case results in an 18% reduction in levelized energy cost. Although these results apply to the specific case tested, it shows the approximate level of tax equalizers necessary to gain parity between solar and conventional technologies.

• Low-Cost Debt
  Finally, a number of institutions have indicated that low-cost debt may be available for renewable power projects. Given the capital intensity of solar technologies, this offers one of the largest opportunities for cost reduction. For example, the availability of 2% debt in place of 9.5% debt could reduce the levelized cost of energy by more than 30%.

Figure 1 summarizes the opportunities for cost reduction in parabolic-trough power technology. These cost reduction opportunities are generally multiplicative, but not all would be taken together. Although cost reduction is often thought to result primarily from the introduction of advanced technologies, it is clear that the most significant opportunities for cost reduction are through non-technology development areas. The largest opportunities result from the type of project financing and the existence of a power park to consolidate construction and O&M costs.

World Bank Cost Reduction Study

The World Bank initiated a study in December 1999 to understand the cost reduction potential of concentrating solar power technologies (Enermodal 1999). The study was in support of the Global Environment Facility (GEF) that provides grants to buy down the non-economic cost of greenhouse gas-reducing technologies. Although the GEF had committed $50 million to a parabolic trough power project in India, they were concerned with the amount of support that would be required to drive the cost of CSP technologies to be competitive with existing fossil power technologies. The study identified parabolic trough technology as the most commercially mature CSP technology and found that troughs appear to offer significant opportunity for continued cost reduction. In addition, there are niche market opportunities due to green power incentives or high fuel prices where the economics may already favor parabolic trough technology. Based on the results of the study, the GEF decided to provide grants for additional projects in Egypt, Morocco, and Mexico. In addition, the GEF has indicated it will consider supporting additional trough plants in the future.

ISCCS Development

The integrated solar combined-cycle system (ISCCS) is a hybrid concept that integrates a parabolic trough solar plant with a combined-cycle plant. Historically, the ISCCS design over-sizes the steam turbine so that the solar energy can be used in the combined cycle's Rankine steam bottoming cycle. This approach effectively reduces the cot of the conventional portion of the plant. The primary concern with this ISCCS approach is that the gas mode efficiency of the combined cycle is reduced when solar energy is not available. Bechtel Corporation, under contract to NREL, has developed a number of new ISCCS designs that do not have a negative impact on the combined cycle's gas-mode-only conversion efficiency. These designs are based on integrating a trough plant into a "merchant" combined-cycle plant (approximately 300 MW). The plant is designed for solar output to offset the normal drop in plant power output as ambient temperatures rise. The design solar contribution is approximately 5% of the total plant output. Because "merchant plants" are already designed to use duct burners to increase the power output of the steam turbine during high ambient temperature condition, no significant changes to the combined-cycle power plant are required. In addition, because adding solar steam improves the use of waste heat from the gas turbine, the apparent solar-to-electric conversion efficiency of solar steam is increased from about 34% (net) in a conventional SEGS plant to more than 45% in at least one of the proposed ISCCS configurations. Other integration approaches, such as generation of high-pressure steam to inject into the gas turbine, have also been evaluated and can be used to help increase the solar contribution in the ISCCS plant. These ISCCS options are one of the most promising near-term options for parabolic trough deployment opportunities in Mexico, the United States, and other locations.

Concentrating Solar Thermal Heating Systems

Solar thermal systems convert sunlight into heat. "Flat-plate" solar thermal collectors produce heat at relatively low temperatures (80 to 140°F [27 to 60°C]), and are generally used to heat air or a liquid for space and water heating or drying agricultural products. Concentrating solar collectors produce higher temperatures. They are most often used where higher temperature heat is desirable, there are large thermal loads, and/or where there are limitations in the area available for installing solar collectors, since they provide more energy per unit of collector surface area. They can also be applied in the production or refining of chemicals and fuels or to produce mechanical or electrical energy. The following is a discussion of concentrating systems for space or water heating. Such collectors can also be used to produce heat for absorption cooling.

There are a variety of types of concentrating solar thermal collectors. They achieve higher temperatures by using a concentrating reflector to direct sunlight from a large area to a smaller receiver and absorber area. A liquid is pumped through the absorber, where it is heated and then sent to a storage system or used directly for heating. Concentrating collectors work best in climates that have a high amount of direct solar radiation. They do not function as well on cloudy days, when available solar radiation is mostly diffuse. The amount of useful heat they produce is mainly a function of the intensity of solar radiation available, the size of the reflector, how well they concentrate solar energy onto the receiver, the characteristics of the absorber, and the control of the flow rate of the heat transfer fluid.

A concentrating collector system can have a fixed or stationary collector, or it can track the sun. In stationary systems the reflector and absorber are in a fixed position, usually oriented directly true south. Tracking devices shift the position of the reflector and the receiver to maximize the amount of sunlight concentrated on the receiver.

Tracking collectors are either single-axis or double-axis. Single-axis tracking devices move the collector on one axis: east to west or north to south. Dual-axis tracking devices track the sun on all axes. The entire collector, containing the reflector and receiver, generally moves as a unit in both types. Systems with dual-axis tracking concentrate solar energy the most and therefore produce the highest temperatures, but are the most complex and expensive.

The most common types of concentrating solar thermal heating collectors are based on the parabolic trough. Parabolic troughs are U-shaped, concentrators that focus sunlight onto a linear receiver tube located along the focal line of the trough. The receiver may be enclosed in a transparent glass tube to reduce heat loss from the absorber and maximize absorption of solar energy. They generally have single-axis tracking.

Another type of concentrating system that is possible to use in a heating application is the parabolic dish. This has a bowl shaped reflector that focuses the sun onto a relatively small receiver. For optimum performance they require dual axis tracking and the receiver moves with the reflector. This complicates their practical application for water and space heating. Most parabolic dish systems are very sophisticated systems used for electricity generation or very simple systems for cooking food on a small-scale. Other types of concentrating systems have an array of reflectors that individually track the sun and focus sunlight onto a central receiver located on a tower. Development of these systems has focused on electric power generation.

There are two basic types of parabolic trough solar heating collectors that have been commercially developed: cylindrical parabolic troughs and compound parabolic collectors.

A standard cylindrical parabolic trough has a fixed receiver/absorber positioned in the middle of the trough at or slightly above the radius across the edges of the reflector. The shape of the trough (rim angle) determines the focal point, and thus the position of the receiver. The reflector surface is usually polished aluminum, aluminized plastic, silvered glass, or stainless steal. The receiver usually has an absorber tube coated with a selective material that has a high absorption for the solar spectrum and low emittance for infrared radiation. The absorber tube may be enclosed in glass with a vacuum to reduce heat loss due to convection and radiation. Receiver temperatures can reach 750°F (400°C).

The trough can be oriented east to west or north to south. They are typically single-axis tracking. When the trough is oriented east to west, the collector moves north to south or south to north as the sun's altitude (height above the horizon) changes throughout the day. When the trough is oriented north to south, the collector moves east to west following the sun's movement across the sky, and returns at sunset to face the sunrise in the morning.

Systems with north-south orientation can be installed so that the collector is at an angle that optimizes performance for different seasons of the year, much like flat-plate solar collectors. For example, if maximum winter performance is preferred, the angle of the collector would be set at 15 degrees plus the site latitude; if summer performance is to be maximized, the angle would be set at 15 degrees less than the site's latitude. An angle equal to the site latitude is a compromise for year round performance.

Most applications of tracking parabolic troughs are relatively large systems to supply heat for domestic water and space heating in commercial and institutional buildings. Examples include the headquarters of the U.S. Department of Agriculture in Washington, DC and at correctional facilities in Phoenix, AZ, Adams County, CO, and Tehachapi, CA. Parabolic solar concentrators are also used for electric power generation at the Solar Electric Generating Systems (SEGS), located in the Mojave Desert at Harper Lake and Kramer Junction, California. The SEGS consist of nine hybrid solar thermal parabolic trough/natural gas turbine power plants. These power plants have a combined generation capacity of 354 MW (peak), and are the largest in the world.

Compound parabolic- or Winston-collectors, have two half-parabolic reflectors with a metal absorber pipe located at the bottom of the trough. The compound parabolic collector funnels solar radiation to the absorber pipe. If oriented from east to west, troughs with low concentration ratios can be stationary. They are able to collect some diffuse, as well as direct, solar radiation. These stationary collectors are efficient for medium temperature uses. These systems are much less common than the cylindrical trough type.

Solar Water Heating Systems

Solar water heating systems use the energy from the sun to heat either water or a heat-transfer fluid in collectors. There are passive systems and active systems. A typical solar water heating system will reduce the need for conventional water heating by at least two-thirds, depending on several factors. 

Sometimes the plumbing from a solar water heating system can connect to a house's existing water heater, which stays inactive as long as the water coming in is hot or hotter than the temperature setting on the indoor water heater. When it falls below this temperature, the home's water heater can kick in to make up the difference. High-temperature solar water heaters can provide energy-efficient hot water and hot water heat for large commercial and industrial facilities. 

Solar Water Heating Systems

Direct Systems

This system uses a pump to circulate potable water from the water storage tank through one or more collectors and back into the tank. The pump is regulated by an electronic controller, an appliance timer, or a photovoltaic panel. 

Indirect Systems

In this system, a heat exchanger heats a fluid that circulates in tubes through the water storage tank, transferring the heat from the fluid to the potable water. 

Thermosiphons

A thermosiphon solar water heating system has a tank mounted above the collector. As the collector heats the water, it rises to the storage tank, while heavier cold water sinks down to the collector. 

Draindown Systems

In cold climates, this system prevents water from freezing in the collector by using electric valves that automatically drain the water from the collector when the temperature drops to freezing. "Drainback systems," a variation of this approach, automatically drain the collector whenever the circulating pump stops. 

Swimming Pool Systems

In solar heated swimming pools, the pool's filter pump pumps water through a solar collector, and the pool itself stores the hot water. 

Cooling and heating your building (home, office, school, hospital, etc.) costs you up to 60%, or more, every month you receive your electric bill. You can eliminate the heating and cooling portion of your electric bill forever, and cool and heat your home with the sun's power with our Solar Heating and Cooling system!   

Our Solar Heating and Cooling system is the cleanest, greenest, and lowest cost method to cool and warm your home or commercial office or other buildings.  Our Solar Heating and Cooling system will eliminate your energy costs for heating and cooling your home, office, school, or any other commercial facility for *free: Requires the purchase of our Solar Heating and Cooling system. Minimum size is 10 tons. You must be located in a qualified geographic location, which means our system must be located to receive direct sunlight.  For qualified customers, we will install the system with little to no money down and you pay for the system with the savings our system provides! 

Solar Absorption Cooling. Solar heat can be used to displace electricity used for cooling. Absorption chillers use a heat source, such as natural gas or hot water from solar collectors, to evaporate the already-pressurized refrigerant from an absorbent/refrigerant mixture. Condensation of vapors provides the same cooling effect as that provided by mechanical cooling systems. Although absorption chillers require electricity for pumping the refrigerant, the amount is very small compared to that consumed by a compressor in a conventional electric air conditioner or refrigerator. Solar Absorption Cooling systems are typically sized to carry the full air conditioning load during sunny periods.

 
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Solar Electric Power Systems (PV)

Solar electric power systems transform sunlight into electricity. Sunlight is an abundant resource. Every minute the sun bathes the Earth in as much energy as the world consumes in an entire year. Solar cells employ special materials called semiconductors that create electricity when exposed to light. Solar electric systems are quiet and easy to use, and they require no fuel other than sunlight. Because they contain no moving parts, they are durable, reliable, and easy to maintain. How It Works Solar cells, also known as photovoltaic (PV) cells, do the work of making electricity. Several types of solar electric technology are under development, but four—crystalline silicon (a form of refined beach sand), thin films, concentrators, and thermophotovoltaics—are illustrative of the range of technologies. Solar cells are connected to a variety of other components to make a solar electric power system. Crystalline Silicon Crystalline silicon solar cells are used in more than half of all solar electric devices. Like most semiconductor devices, they include a positive layer (on the bottom) and a negative layer (on the top) that create an electrical field inside the cell. When a photon of light strikes a semiconductor, it releases electrons (see animation). The free electrons flow through the solar cell's bottom layer to a connecting wire as direct current (DC) electricity. Some solar cells are made from polycrystalline silicon, which consists of several small silicon crystals. Polycrystalline silicon solar cells are cheaper to produce but somewhat less efficient than single-crystal silicon. A simple silicon solar cell can power a watch or calculator. However, it produces only a tiny amount of electricity. Connected together, solar cells form modules that can generate substantial amounts of power. Modules are the building blocks of solar electric systems, which can produce enough power for a house, a rural medical clinic, or an entire village. Large arrays of solar electric modules can power satellites or provide electricity for utilities. Solar Electric Power System Components In addition to modules, several components are needed to complete a solar electric power system. Many systems include batteries, battery chargers, a backup generator, and a controller so that people in solar-powered homes and buildings can turn on the lights at night or run televisions or appliances on cloudy days. Grid-connected systems don't require batteries or backup generators because they use the grid for backup power. Some remote system applications, such as those used to pump water, do not require a backup power source. Components of a typical standalone PV system using crystalline silicon technology. (Source: Solar Electric Power Association) Solar electric power systems can incorporate inverters or power control units to transform the DC electricity produced by the solar cells into alternating current (AC) to run AC appliances or sell to a utility grid. Complete systems usually include safety disconnects, fuses, and a grounding circuit as well. Thin Films Solar electric thin films are lighter, more resilient, and easier to manufacture than crystalline silicon modules. The best-developed thin-film technology uses amorphous silicon, in which the atoms are not arranged in any particular order as they would be in a crystal. An amorphous silicon film only one micron thick can absorb 90% of the usable solar energy falling on it. Other thin-film materials include cadmium telluride and copper indium diselenide. Substantial cost savings are possible with this technology because thin films require relatively little semiconductor materials. Thin films are produced as large, complete modules, not as individual cells that must be mounted in frames and wired together. They are manufactured by applying extremely thin layers of semiconductor material to a low-cost backing such as glass or plastic. Electrical contacts, antireflective coatings, and protective layers are also applied directly to the backing material. Thin films conform to the shape of the backing, a feature that allows them to be used in such innovative products as flexible solar electric roofing shingles. Concentrators Concentrators use optical lenses (similar to plastic magnifying glasses) or mirrors to concentrate the sunlight that falls on a solar cell. With a concentrator to magnify the light intensity, the solar cell produces more electricity. Today, most solar cells in concentrators are made from crystalline silicon. However, materials such as gallium arsenide and gallium indium phosphide are more efficient than silicon in solar electric concentrators and will likely see more use in the future. These materials are now used in communications satellites and other space applications. Concentrators produce more electricity using less of the expensive semiconductor material than other solar electric systems. A basic concentrator unit consists of a lens to focus the light, a solar cell assembly, a housing element, a secondary concentrator to reflect off-center light rays onto the cell, a mechanism to dissipate excess heat, and various contacts and adhesives. The basic unit can be combined into modules of varying sizes and shapes. Concentrators only work with direct sunlight and operate most effectively in sunny, dry climates. They must be used with tracking systems to keep them pointed toward the sun. Thermophotovoltaics Thermophotovoltaic (TPV) devices convert heat into electricity in much the same way that other PV devices convert light into electricity. The difference is that TPV technology uses semiconductors "tuned" to the longer-wavelength, invisible infrared radiation emitted by warm objects. This technology is cleaner, quieter, and simpler than conventional power generation using steam turbines and generators. TPV converters are relatively maintenance-free because they contain no moving parts. In addition to using solar energy, they can convert heat from any high-temperature heat source, including combustion of a fuel such as natural gas or propane, into electricity. TPV converters produce virtually no carbon monoxide and few emissions. They may be used in the future in gas furnaces that generate their own electricity for self-ignition (during power outages) and in portable generators and battery chargers. Advantages Solar electric systems offer many advantages. Standalone systems can eliminate the need to build expensive new power lines to remote locations. For rural and remote applications, solar electricity can cost less than any other means of producing electricity. Solar electric systems can also connect to existing power lines to boost electricity output during times of high demand such as on hot, sunny days when air conditioners are on. Solar electric systems are flexible. Solar electric modules can stand on the ground or be mounted on rooftops. They can also be built into glass skylights and walls. They can be made to look like roof shingles and can even come equipped with devices to turn their DC output into the same AC utilities deliver to wall sockets. These advances mean individual homeowners and businesses can relieve pressure on local utilities struggling to meet the increasing demand for electricity. More than 30 states offer grid-connected solar electric system owners the chance to save money on their energy bills by feeding any excess power their solar electric system produces into the utility grid—an arrangement called net metering. Solar power systems require minimal maintenance. They run quietly and efficiently without polluting. They are easy to combine with other types of electric generators such as wind, hydro, or natural gas turbines. They can charge batteries to make solar electricity continuously available. For utilities, large-scale solar electric power plants can help meet demand for new power generation, especially in distributed applications. A solar electric power plant is created from multiple arrays that are interconnected electronically. Solar electric plants are easier to site and are quicker to build than conventional power plants. They are also easy to expand incrementally—by adding more modules—as power demand increases. Solar electric power systems are good for the environment. When solar electric technologies displace fossil fuels for pumping water, lighting homes, or running appliances, they reduce the greenhouse gases and pollutants emitted into the atmosphere. The use of solar electric systems is particularly important in developing nations because it can help avert the expected increases in emissions of greenhouse gases caused by the growing demand for electricity in those countries. Solar electric technologies also benefit the U.S. economy by creating jobs in U.S. companies. Exporting solar electric technologies to developing nations expands U.S. markets while protecting the global environment. Disadvantages Although solar electric systems make financial sense in remote areas that lack access to power lines, they are usually more expensive than fossil fuels for grid-connected applications. This disadvantage is significant for utilities considering large-scale solar electric power plants. Although solar electricity costs considerably more than electricity generated by conventional plants, regulatory agencies often require utilities to supply electricity for the lowest cash cost. Utilities view solar electric power plants differently than they view conventional power plants. Solar electric modules produce electricity intermittently—only when the sun shines. Their output varies with the weather and disappears altogether at night. Integrating solar electricity into a utility system requires creative planning. Applications A combination of solar electric arrays and pool-heating solar collectors were used to provide power and heat to the Georgia Tech University Aquatic Center, site of the 1996 Olympic swimming competition. (Credit: Heliocol) Solar electricity has powered satellites since the dawn of the space program. It has run remote communications outposts high in the mountains and turned on the lights, kept medicines cold, and pumped water in rural areas for more than 30 years. Small solar cells are used to power wristwatches, calculators, and other electronic gadgets. More recently, solar electric systems have been used to provide supplemental power to homes and commercial buildings in cities. Solar electric technology has important roles to play in both the developing and developed worlds. From the farmer irrigating his crops in rural Mexico to an innovative lighting system for an Olympic sports arena, solar electric solutions abound. Electric utilities harness solar electricity for distributed applications—near substations or at the end of overloaded power lines, for example, to avoid or defer costly line upgrades. They use solar electricity during hot, sunny periods when the demand for air conditioning stretches conventional power generation to its limit. The Sacramento Municipal Utility District, for example, uses large solar electric arrays as part of its power generation mix. Utilities also rely on solar electricity to power remote, standalone monitoring systems. Consumers and builders are integrating solar electric modules into their homes and offices. Innovative solar electric technologies can replace conventional roofing and facade materials in new buildings. Solar electric roofing shingles, for example, are being used in some new residences. In grid-connected applications, solar electricity supplies some of a consumer's energy needs; the local utility provides the rest. Standalone solar electric systems power a variety of applications far from the reaches of the power grid. These applications include remote communications systems such as television and radio transmitters and receivers, telephone systems, and microwave repeaters. Standalone solar electric power is also used to prevent corrosion of metal pipes, tanks, bridges, and buildings. Many remote residences worldwide use solar electricity as their source of power. For instance, more than 100,000 vacation homes in Scandinavia rely solely on solar electric technology to run lights and appliances. Villages around the world are building solar electric systems to bring electricity to their homes and local industries, often for the first time. To make the maximum use of available resources, village power is typically produced by a hybrid power system that combines solar electricity with diesel backup generators and sometimes another renewable energy technology such wind power. Villages also use standalone solar electric systems for pumping water—an application shared by rural farmers and ranchers in the United States. For more information, visit the following Web sites: DOE Solar Energy Technologies Program — information about the DOE program, solar electric technologies, and applications DOE's National Center for Photovoltaics — detailed information about DOE research Energy Efficiency and Renewable Energy Clearinghouse PV fact sheet (PDF 264 KB) Download Acrobat Reader. — information about designing a solar electric system NREL's Clean Energy Basics — more background on solar electricity, including information specifically aimed at homeowners, small business owners, electricity providers, and teachers.

Our Solar Heating and Cooling System - Uses the "free" Power of the Sun to Heat and Cool your Commercial Business or Home for Free!

Cooling and heating your building (home, office, school, hospital, etc.) costs you up to 60%, or more, every month you receive your electric bill. You can eliminate the heating and cooling portion of your electric bill forever, and cool and heat your home with the sun's power with our Solar Heating and Cooling system!   

Our Solar Heating and Cooling system is the cleanest, greenest, and lowest cost method to cool and warm your home or commercial office or other buildings.  Our Solar Heating and Cooling system will eliminate your energy costs for heating and cooling your home, office, school, or any other commercial facility for *free: Requires the purchase of our Solar Heating and Cooling system. Minimum size is 10 tons. You must be located in a qualified geographic location, which means our system must be located to receive direct sunlight.  For qualified customers, we will install the system with little to no money down and you pay for the system with the savings our system provides! 

Solar Absorption Cooling. Solar heat can be used to displace electricity used for cooling. Absorption chillers use a heat source, such as natural gas or hot water from solar collectors, to evaporate the already-pressurized refrigerant from an absorbent/refrigerant mixture. Condensation of vapors provides the same cooling effect as that provided by mechanical cooling systems. Although absorption chillers require electricity for pumping the refrigerant, the amount is very small compared to that consumed by a compressor in a conventional electric air conditioner or refrigerator. Solar Absorption Cooling systems are typically sized to carry the full air conditioning load during sunny periods. 

Let Us Help You Design, Install and Buy Your Combination
Solar Electric Power and Heating & Cooling System System

Call us at 832-758-0027
or e-mail us at:  sales@cogeneration.net for more information

How Does an Absorption Chiller Work?

What is an Absorption Chiller?

Absorption chillers use heat instead of mechanical energy to provide cooling. A thermal compressor consists of an absorber, a generator, a pump, and a throttling device, and replaces the mechanical vapor compressor.

In the chiller, refrigerant vapor from the evaporator is absorbed by a solution mixture in the absorber. This solution is then pumped to the generator. There the refrigerant re-vaporizes using a waste steam heat source. The refrigerant-depleted solution then returns to the absorber via a throttling device. The two most common refrigerant/ absorbent mixtures used in absorption chillers are water/lithium bromide and ammonia/water.

Compared with mechanical chillers, absorption chillers have a low coefficient of performance (COP = chiller load/heat input). However, absorption chillers can substantially reduce operating costs because they are powered by low-grade waste heat. Vapor compression chillers, by contrast, must be motor- or engine-driven.

Low-pressure, steam-driven absorption chillers are available in capacities ranging from 100 to 1,500 tons. Absorption chillers come in two commercially available designs: single-effect and double-effect. Single-effect machines provide a thermal COP of 0.7 and require about 18 pounds of 15-pound-per-square-inch-gauge (psig) steam per ton-hour of cooling. Double-effect machines are about 40% more efficient, but require a higher grade of thermal input, using about 10 pounds of 100- to 150-psig steam per ton-hour.

A single-effect absorption machine means all condensing heat cools and condenses in the condenser. From there it is released to the cooling water. A double-effect machine adopts a higher heat efficiency of condensation and divides the generator into a high-temperature and a low-temperature generator.

Is It Right for You?

Absorption cooling may be worth considering if your site requires cooling, and if at least one of the following applies:

• You have a combined heat and power CHP) unit and cannot use all of the available heat, or if you are considering a new CHP plant

• Waste heat is available

• A low-cost source of fuels is available

• Your boiler efficiency is low due to a poor load factor

• Your site has an electrical load limit that will be expensive to upgrade

• Your site needs more cooling, but has an electrical load limitation that is expensive to overcome, and you have an adequate supply of heat.

In short, absorption cooling may fit when a source of free or low-cost heat is available, or if objections exist to using conventional refrigeration. Essentially, the low-cost heat source displaces higher-cost electricity in a conventional chiller.

In Practice

In a plant where low-pressure steam is currently being vented to the atmosphere, a mechanical chiller with a COP of 4.0 is used 4,000 hours a year to produce an average 300 tons of refrigeration. The plant's cost of electricity is $0.05 a kilowatt-hour. 

An absorption unit requiring 5,400 lbs/hr of 15-psig steam could replace the mechanical chiller, providing annual electrical cost savings of:

Annual Savings = 300 tons x (12,000 Btu/ton / 4.0) x 4,000 hrs/yr x $0.05/kWh x kWh/3,413 Btu = $52,740

Actions You Can Take

Determine the cost-effectiveness of displacing a portion of your cooling load with a waste steam absorption chiller by taking the following steps:

• Conduct a plant survey to identify sources and availability of waste steam

• Determine cooling load requirements and the cost of meeting those requirements with existing mechanical chillers or new installations

• Obtain installed cost quotes for a waste steam absorption chiller

• Conduct a life cycle cost analysis to determine if the waste steam absorption chiller meets your company's cost-effectiveness criteria.

Absorption Chiller Refrigeration Cycle

The basic cooling cycle is the same for the absorption and electric chillers. Both systems use a low-temperature liquid refrigerant that absorbs heat from the water to be cooled and converts to a vapor phase (in the evaporator section). The refrigerant vapors are then compressed to a higher pressure (by a compressor or a generator), converted back into a liquid by rejecting heat to the external surroundings (in the condenser section), and then expanded to a low- pressure mixture of liquid and vapor (in the expander section) that goes back to the evaporator section and the cycle is repeated.

The basic difference between the electric chillers and absorption chillers is that an electric chiller uses an electric motor for operating a compressor used for raising the pressure of refrigerant vapors and an absorption chiller uses heat for compressing refrigerant vapors to a high-pressure. The rejected heat from the power-generation equipment (e.g. turbines, microturbines, and engines) may be used with an absorption chiller to provide the cooling in a CHP system.

The basic absorption cycle employs two fluids, the absorbate or refrigerant, and the absorbent. The most commonly fluids are water as the refrigerant and lithium bromide as the absorbent. These fluids are separated and recombined in the absorption cycle. In the absorption cycle the low-pressure refrigerant vapor is absorbed into the absorbent releasing a large amount of heat. The liquid refrigerant/absorbent solution is pumped to a high-operating pressure generator using significantly less electricity than that for compressing the refrigerant for an electric chiller. Heat is added at the high-pressure generator from a gas burner, steam, hot water or hot gases. The added heat causes the refrigerant to desorb from the absorbent and vaporize. The vapors flow to a condenser, where heat is rejected and condense to a high-pressure liquid. The liquid is then throttled though an expansion valve to the lower pressure in the evaporator where it evaporates by absorbing heat and provides useful cooling. The remaining liquid absorbent, in the generator passes through a valve, where its pressure is reduced, and then is recombined with the low-pressure refrigerant vapors returning from the evaporator so the cycle can be repeated.

Absorption chillers are used to generate cold water (44°F) that is circulated to air handlers in the distribution system for air conditioning.

"Indirect-fired" absorption chillers use steam, hot water or hot gases steam from a boiler, turbine or engine generator, or fuel cell as their primary power input. Theses chillers can be well suited for integration into a CHP system for buildings by utilizing the rejected heat from the electric generation process, thereby providing high operating efficiencies through use of otherwise wasted energy.

"Direct-fired" systems contain natural gas burners; rejected heat from these chillers can be used to regenerate desiccant dehumidifiers or provide hot water.

Commercially absorption chillers can be single-effect or multiple-effect. The above schematic refers to a single-effect absorption chiller. Multiple-effect absorption chillers are more efficient and discussed below.

Multiple-Effect Absorption Chillers

In a single-effect absorption chiller, the heat released during the chemical process of absorbing refrigerant vapor into the liquid stream, rich in absorbent, is rejected to the environment. In a multiple-effect absorption chiller, some of this energy is used as the driving force to generate more refrigerant vapor. The more vapor generated per unit of heat or fuel input, the greater the cooling capacity and the higher the overall operating efficiency.

A double-effect chiller uses two generators paired with a single condenser, absorber, and evaporator. It requires a higher temperature heat input to operate and therefore they are limited in the type of electrical generation equipment they can be paired with when used in a CHP System.

Triple-effect chillers can achieve even higher efficiencies than the double-effect chillers. These chillers require still higher elevated operating temperatures that can limit choices in materials and refrigerant/absorbent pairs. Triple-effect chillers are under development by manufacturers working in cooperation with the U.S. Department of Energy.

* Geothermal Energy... Power from the Depths

The Earth's crust is a bountiful source of energy—and fossil fuels are only part of the story. Heat or thermal energy is by far the more abundant resource. To put it in perspective, the thermal energy in the uppermost six miles of the Earth's crust amounts to 50,000 times the energy of all oil and gas resources in the world!

The word "geothermal" literally means "Earth" plus "heat." The geothermal resource is the world's largest energy resource and has been used by people for centuries. In addition, it is environmentally friendly. It is a renewable resource and can be used in ways that respect rather than upset our planet's delicate environmental balance.

Geothermal power plants operating around the world are proof that the Earth's thermal energy is readily converted to electricity in geologically active areas. Many communities, commercial enterprises, universities, and public facilities in the western United States are heated directly with the water from underground reservoirs. For the homeowner or building owner anywhere in the United States, the emergence of geothermal heat pumps brings the benefits of geothermal energy to everyone's doorstep.

The Basics

There's a relatively simple concept underlying all the ways geothermal energy is used: The flow of thermal energy is available from beneath the surface of the Earth and especially from subterranean reservoirs of hot water. Over the years, technologies have evolved that allow us to take advantage of this heat.

In fact, electric power plants driven by geothermal energy provide over 44 billion kilowatt hours of electricity worldwide per year, and world capacity is growing at approximately 9% per year. To produce electric power from geothermal resources, underground reservoirs of steam or hot water are tapped by wells and the steam rotates turbines that generate electricity. Typically, water is then returned to the ground to recharge the reservoir and complete the renewable energy cycle.

Underground reservoirs are also tapped for "direct-use" applications. In these instances, hot water is channeled to greenhouses, spas, fish farms, and homes to fill space heating and hot water needs.

Geothermal energy use extends beyond underground reservoirs. The soil and near-surface rocks, from 5 to 50 feet deep, have a nearly constant temperature from geothermal heating. As a homeowner or business owner, you can use the Earth as a heat source or heat sink with geothermal heat pumps. According to the U.S. Environmental Protection Agency (EPA), geothermal heat pumps are one of the nation's most efficient—and therefore least polluting—heating, cooling, and water-heating systems available. In winter, these systems draw on "earth heat" to warm the house, and in summer they transfer heat from the house to the earth, which ranges in temperature from 50° to 70°F (10° to 21°C) depending on latitude.

A Clear Advantage

Geothermal energy delivers some powerful environmental and economic benefits. If you live in an area that uses geothermal resources for electricity production, you're quite fortunate. Consider Lake County, California, which is home to many of the geothermal power plants at our nation's best-developed geothermal resource, The Geysers. It's no coincidence that the Lake County air basin is the first and only one in compliance with all of California's stringent air quality regulations.

Perhaps you own a greenhouse and need to cut exorbitant energy bills in order to stay in business. If you are located near a geothermal resource, you should know that most greenhouse growers estimate that direct use of geothermal resources instead of traditional energy sources reduces heating costs by up to 80%. This can save about 5% to 8% in total operating cost.

Assume you're a home or business owner who has installed a geothermal heat pump. You're not only doing your part to help make the world a cleaner place to live and breathe, you're rewarded with low operating and maintenance costs, and, usually, lowest life-cycle costs. (Life-cycle cost is the total cost of the equipment spread over the useful life of the equipment.) In practical terms, your heat pump investment may cost you $15 per month more in mortgage payments, but it may save you $30 per month on your electric bill.

In all three of these cases, domestic, not foreign, resources are being used—a practice that has merits all its own. Nearly half of our nation's annual trade deficit would be obliterated if we could displace imported oil with domestic energy resources. A nation's trade deficit represents a permanent loss of wealth for the citizens of that nation. Keeping the wealth at home translates to more jobs and a robust economy. And not only does our national economic and employment picture improve, but a vital measure of national security is gained when we control our own energy supplies.

Types of Geothermal Resources

The center of the Earth is 4000 miles (6400 kilometers) deep. How hot is this region? Our best guess is 7200°F (4000°C) or higher. Partially molten rock, at temperatures between 1200° and 2200°F (650° to 1200°C), is believed to exist at depths of 50 to 60 miles (80 to 100 kilometers).

Heat is constantly flowing from the Earth's interior to the surface. Most types of geothermal resources—hydrothermal, geopressured, hot dry rock, and magma—result from concentration of Earth's thermal energy within certain discrete regions of the subsurface.

Hydrothermal resources are reservoirs of steam or hot water, which are formed by water seeping into the earth and collecting in, and being heated by fractured or porous hot rock. These reservoirs are tapped by drilling wells to deliver hot water to the surface for generation of electricity or direct use. Hot water resources exist in abundance around the world. In the United States, the hottest (and currently most valuable) resources are located in the western states, and Alaska and Hawaii. Technologies to tap hydrothermal resources are proven commercial processes.

Geopressured resources are deeply buried waters at moderate temperature that contain dissolved methane. While technologies are available to tap geopressured resources, they are not currently economically competitive. In the United States, this resource base is located in the Gulf coast regions of Texas and Louisiana.

Hot dry rock resources occur at depths of 5 to 10 miles (8 to 16 kilometers) everywhere beneath the Earth's surface, and at shallower depths in certain areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rock, and drawing off the now hot water from another well. This promising technology has been proven feasible, but no commercial applications are in use at this time.

Magma (or molten rock) resources offer extremely high-temperature geothermal opportunities, but existing technology does not allow recovery of heat from these resources.

Earth energy is the heat contained in soil and rocks at shallow depths. This resource is tapped by geothermal heat pumps.

Geothermal Power Plants—from Water to Light

Flip a switch and light up a room—what could be easier? Push a button on the TV remote control and be entertained. It all seems so simple that we are often unaware of the true environmental and social cost of these conveniences—and who would want to give them up even if we had to account for every penny?

But rather than thinking in terms of giving things up, let's think positively: in the United States, right now, the installed generating capacity for geothermal stands at about 2700 megawatts. That's the equivalent of about 58 million barrels of oil, and provides enough electricity for 3.7 million people. The cost of producing this power ranges from 4¢ to 8¢ per kilowatt hour. The geothermal industry is working to achieve a geothermal life-cycle energy cost of 3¢ per kilowatt hour. And remember, this is clean energy produced from domestic resources.

How clean? In terms of air emissions, geothermal power plants have an inherent advantage over fossil fuel plants because no combustion takes place. Geothermal plants emit no nitrogen oxides and very low amounts of sulfur dioxide—allowing them to easily meet the most stringent clean air standards. The steam at some steam plants contains hydrogen sulfide, but treatment processes remove more than 99.9% of those emissions. Typical emissions of hydrogen sulfide from geothermal plants are less than 1 part per billion—well below what people can smell. The low levels of air emissions produced are mostly carbon dioxide, which many people believe acts as a greenhouse gas to trap heat within Earth's atmosphere. Even so, geothermal plants emit minimal amounts of carbon dioxide—1/1000 to 1/2000 of the amount produced by fossil-fuel plants.

Geothermal water sometimes contains salts and dissolved minerals. In the United States, the geothermal water is usually injected back into the reservoir from where it came, at a depth well below groundwater aquifers, after its heat energy has been extracted. This recycles the geothermal water and replenishes the reservoir. However, some geothermal plants also produce some solid materials, or sludges, that require disposal in approved sites.

All U.S. geothermal power plants are located in the states of California, Nevada, Utah, and Hawaii—home to some of the most majestic scenery on Earth. It's fortunate, then, that these plants consume only a small amount of land, and can coexist with numerous other land uses, including agriculture, with minimal impact on the surrounding beauty.

They're reliable and efficient, too. Taken as a group, geothermal power plants are available to generate power 95% or more of the time; they are seldom off-line for maintenance or repair. And, they have the highest capacity factors of all types of power plants. Capacity factor is the ratio of the amount of electricity a plant produces to how much electricity it is capable of producing.

Dry Steam Power Plants were the first type of geothermal power plant (in Italy in 1904). The Geysers in northern California, which is the world's largest single source of geothermal power, is also home to this type of plant. These plants use the steam as it comes from wells in the ground, and direct it into the turbine/generator unit to produce power.

Flash Steam Power Plants, which are the most common, use water with temperatures greater than 360°F (182°C). This very hot water is pumped under high pressure to equipment on the surface, where the pressure is suddenly dropped, allowing some of the hot water to "flash" into steam. The steam is then used to power the turbine/generator. The remaining hot water and condensed steam are injected back into the reservoir.

Binary Cycle Power Plants operate on the lower-temperature waters, 225° to 360°F (107° to 182°C). These plants use the heat of the hot water to boil a "working fluid," usually an organic compound with a low boiling point. This working fluid is then vaporized in a heat exchanger and used to turn a turbine. The geothermal water and the working fluid are confined to separate closed loops, so there are no emissions into the air.

Because these lower-temperature waters are much more plentiful than high-temperature waters, binary cycle systems will be the dominant geothermal power plants of the future.

Developing and commercializing geothermal power technologies contributes not only to a cleaner environment, but to a healthy U.S. industrial base, as well. Around the developing countries of the world, demand for electric power is burgeoning—and nearly half of these countries have geothermal resources. These markets have proven particularly receptive to clean energy produced with indigenous resources, creating attractive export options for geothermal technologies and expertise. In fact, U.S. geothermal companies have signed contracts worth more than $6 billion in the past few years to build geothermal power plants in some of these developing countries.

Direct Use of Geothermal Energy

If you've ever soaked in water from a natural hot spring, you're one of the millions of people around the world who has enjoyed the direct use of geothermal energy. And while this naturally occurring hot water may be the perfect tonic for frayed nerves and sore muscles, it's capable of much more. In the United States alone, direct geothermal applications (not including geothermal heat pumps) have an installed capacity of 500 thermal megawatts, which is roughly equivalent to saving half a million barrels of oil per year. This includes approximately 40 greenhouses, 30 fish farms, 190 resorts and spas, 125 space and district heating projects, and 10 industrial projects.

The resource required for these applications is widespread across the western third of the United States. This is water in an underground reservoir, at low-to-moderate temperatures usually ranging from 68° to 302°F (20° to 150°C). The consumer of direct-use geothermal energy can count on savings in energy costs—as much as an 80% reduction from traditional fuel costs, depending on the application and the industry. Direct-use systems typically require a larger initial investment, but have lower operating costs and no need for ongoing fuel purchases, therefore reducing life-cycle costs.

In a typical application, a well brings heated water to the surface; a mechanical system—piping, heat exchanger, controls—delivers the heat to the space or process; and a disposal system either injects the cooled geothermal fluid underground or disposes of it on the surface.

The direct use of geothermal energy offers some heartening possibilities. Imagine an entire community of people having their homes heated geothermally. Sound like something way off in the future? Not at all. In 1893, the citizens of Boise, Idaho, put their pioneering spirit to work and built the world's first geothermal district heating system by piping water from a nearby hot spring. Within a few years, the system was providing heat to 200 homes and 40 downtown businesses—and the system continues to flourish today.

There are now 18 district heating systems in the United States (including one in Klamath Falls, Oregon, that melts snow from the city's downtown sidewalks), and the potential for more is tremendous. A recently updated resource inventory of 10 western states identified 271 communities located within 5 miles (8 kilometers) of a geothermal resource.

Greenhouse operators are taking advantage of geothermal direct use in growing numbers, with nearly 40 greenhouses (many of which are several acres in size) producing vegetables, flowers, houseplants, and tree seedlings in eight western states. Operators of fish farms are profiting from the lower energy costs and improved fish growth rates that geothermal energy delivers. Other industrial and commercial applications that match well with geothermal direct use include food dehydration, laundries, gold processing, milk pasteurizing, and swimming pools and spas.

The Heat Pump Solution

The geothermal heat pump doesn't create electricity—but it greatly reduces consumption of it. If you would like to reduce the cost of heating and cooling your home, you might want to consider installing a geothermal heat pump, an economical and energy-efficient technology for space heating and cooling and water heating. Nationwide, more than 350,000 of these systems are in operation in homes, schools, and businesses. And the geothermal heat pump industry expects to be installing 40,000 systems per year by 2000.

In winter, heat pump systems draw thermal energy from the ambient temperature of the shallow ground, which ranges between 50° and 70°F (10° to 21°C ) depending on latitude. In summer, the process is reversed to a cooling mode, using the ground as a sink for the heat contained within the building. The system does not convert electricity to heat; rather, it uses electricity to move thermal energy between the building and the ground and condition it to a higher or lower temperature according to the heating or cooling requirements. Consumption of electricity is reduced 30% to 60% compared to traditional heating and cooling systems, allowing a payback of system installation in 2 to 10 years. And these low-maintenance systems have long lives of 30 years or more. Some systems are also capable of producing domestic hot water at no cost in summer and at small cost in winter.

An analysis by the EPA found these systems to be among the most efficient space-conditioning technologies available—with the lowest environmental cost of all that were analyzed. But this might be the most compelling statistic: Surveys show that the number of satisfied geothermal heat pump customers stands at 95% or higher.

About Solar Heating and Cooling

It is possible to use solar thermal energy or solar electricity to operate or power an HVAC or heating and cooling system.  The following is a brief description of "active" solar cooling and refrigeration technologies. Active solar energy systems use a mechanical or electrical device to transfer solar energy absorbed in a solar collector to another component in the "system." It is possible to also cool a building or structure by using the natural processes of solar heat transfer (conduction, convection, and radiation). This is often referred to as "passive solar cooling," and is primarily an architectural technique. This brief focuses on active solar cooling systems. The American Solar Energy Society (ASES, see Source List below) is one source of information on passive solar cooling techniques.

Absorption Cooling and Refrigeration

Absorption cooling is the first and oldest form of air conditioning and refrigeration. An absorption air conditioner or refrigerator does not use an electric compressor to mechanically pressurize the refrigerant. Instead, the absorption device uses a heat source, such as natural gas or a large solar collector, to evaporate the already-pressurized refrigerant from an absorbent/refrigerant mixture. This takes place in a device called the vapor generator. Although absorption coolers require electricity for pumping the refrigerant, the amount is small compared to that consumed by a compressor in a conventional electric air conditioner or refrigerator. When used with solar thermal energy systems, absorption coolers must be adapted to operate at the normal working temperatures for solar collectors: 180° to 250°F (82° to 121°C). It is also possible to produce ice with a solar powered absorption device, which can be used for cooling or refrigeration.

How Does an Engine Driven Chiller Work?

Packaged natural gas engine-driven water chillers and direct expansion (DX) units are now available. Commercially proven custom and packaged engine-driven refrigeration units offer excellent reliability and economic advantages for ice rinks, refrigerated warehouses and other applications. The industry is also focusing on developing small, engine-driven heating and cooling systems suitable for small commercial applications.

Operation: Engine-driven cooling systems employ a conventional vapor compression cycle. Their main components are the compressor, condenser, expansion valve and evaporator.

 Advantages: The main difference between a natural gas and conventional electric system is the replacement of the electric motor with a gas engine. This change results in variable-speed operation capability; higher part-load efficiency; efficient high-temperature waste-heat recovery for water heating, process heating, or steam generation; and an overall reduction in operating expenses.

* Requires no more room than conventional electric chillers

* Lowest operating cost of any available chiller

* Depending on electric rates and natural gas rates, an engine driven chiller may operate at up to 1/2 of the cost of direct-fired absorption chillers

* Like absorption chillers, engine driven chillers reduce on-peak electric demand charges.

* Depending on your electric and/or natural gas supplier, there may be rebates available for purchasing a new absorption chiller or engine driven chiller from your utility supplier. 

* Environmentally friendly.

For more information: call Monty Goodell at: 832-758-0027

* Some of the above information from the Department of Energy website with permission.

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