Cogeneration Technologies
An EcoGeneration Solutions
LLC. Company

E-mail:     info @ cogeneration dot net
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Watersource Heat Pumps
www.WaterSourceHeatPumps.com


Cogeneration Technologies, is based in Houston, Texas and provides 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 are specialists in Renewable Energy Technologies, Demand Side Management and in developing clean power/energy projects that will generate a Renewable Energy CreditCarbon Dioxide Credits and/or 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.

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

 

WaterSource Heat Pumps

Two commercial 36-ton geothermal heat pumps being used at the College of Southern Idaho.
Two 36-ton geothermal heat pumps.

The geothermal heat pump, also known as the ground source heat pump, water-source heat pump, and earth-coupled heat pump, is a highly efficient renewable energy technology that is gaining wide acceptance for both residential and commercial buildings. Geothermal heat pumps are used for space heating and cooling, as well as water heating. Its great advantage is that it works by concentrating naturally existing heat, rather than by producing heat through combustion of fossil fuels.

The technology relies on the fact that the Earth (beneath the surface) remains at a relatively constant temperature throughout the year, warmer than the air above it during the winter and cooler in the summer, very much like a cave. The geothermal heat pump takes advantage of this by transferring heat stored in the Earth or in ground water into a building during the winter, and transferring it out of the building and back into the ground during the summer. The ground, in other words, acts as a heat source in winter and a heat sink in summer.

The system includes three principal components:

  • Geothermal earth connection subsystem

  • Geothermal heat pump subsystem

  • Geothermal heat distribution subsystem.

Earth Connection

Using the Earth as a heat source/sink, a series of pipes, commonly called a "loop," is buried in the ground near the building to be conditioned. The loop can be buried either vertically or horizontally. It circulates a fluid (water, or a mixture of water and antifreeze) that absorbs heat from, or relinquishes heat to, the surrounding soil, depending on whether the ambient air is colder or warmer than the soil.

Heat Pump

For heating, a geothermal heat pump removes the heat from the fluid in the Earth connection, concentrates it, and then transfers it to the building. For cooling, the process is reversed.

Heat Distribution

Conventional ductwork is generally used to distribute heated or cooled air from the geothermal heat pump throughout the building.

Residential Hot Water

In addition to space conditioning, geothermal heat pumps can be used to provide domestic hot water when the system is operating. Many residential systems are now equipped with desuperheaters that transfer excess heat from the geothermal heat pump's compressor to the house's hot water tank. A desuperheater provides no hot water during the spring and fall when the geothermal heat pump system is not operating; however, because the geothermal heat pump is so much more efficient than other means of water heating, manufacturers are beginning to offer "full demand" systems that use a separate heat exchanger to meet all of a household's hot water needs. These units cost-effectively provide hot water as quickly as any competing system.

 

 

Types of Geothermal Heat Pump Systems

There are four basic types of ground loop systems. Three of these—horizontal, vertical, and pond/lake—are closed-loop systems. The fourth type of system is the open-loop option. Which one of these is best depends on the climate, soil conditions, available land, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications.

Closed-Loop Systems

Horizontal

This type of installation is generally most cost-effective for residential installations, particularly for new construction where sufficient land is available. It requires trenches at least four feet deep. The most common layouts either use two pipes, one buried at six feet, and the other at four feet, or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench. The Slinky™ method of looping pipe allows more pipe in a shorter trench, which cuts down on installation costs and makes horizontal installation possible in areas it would not be with conventional horizontal applications.

Illustration of a horizontal closed loop system shows the tubing leaving the house and entering the ground, then branching into three rows in the ground, with each row consisting of six overlapping vertical loops of tubing. At the end of the rows, the tubes are routed back to the start of the rows and combined into one tube that runs back to the house.

Vertical

Large commercial buildings and schools often use vertical systems because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping. For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100–400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold), placed in trenches, and connected to the heat pump in the building.

Illustration of a vertical closed loop system shows the tubing leaving a building and entering the ground, then branching off into four rows in the ground. In each row, the tubing stays horizontal except for departing on three deep vertical loops. At the end of the row, the tubing loops back to the start of the row and combines into one tube that runs back to the building.

Pond/Lake

If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing. The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria.

Illustration of a pond or lake closed loop system shows the tubing leaving the house and entering the ground, then extending to a pond or lake. The tubing drops deep into the pond or lake and then loops horizontally in seven large overlapping loops, then returns to the water's edge, extends up near the surface, and returns back to the house.

Open-Loop System

This type of system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is obviously practical only where there is an adequate supply of relatively clean water, and all local codes and regulations regarding groundwater discharge are met.

Illustration of an open loop system shows a tube carrying water out of the house, into the ground, and over to a well, where it discharges into the groundwater. A separate tube in a well some distance away draws water from the well and returns it to the house.

 

 

Benefits of Geothermal Heat Pump Systems

The biggest benefit of GHPs is that they use 25%–50% less electricity than conventional heating or cooling systems. This translates into a GHP using one unit of electricity to move three units of heat from the earth. According to the EPA, geothermal heat pumps can reduce energy consumption—and corresponding emissions—up to 44% compared to air-source heat pumps and up to 72% compared to electric resistance heating with standard air-conditioning equipment. GHPs also improve humidity control by maintaining about 50% relative indoor humidity, making GHPs very effective in humid areas.

Geothermal heat pump systems allow for design flexibility and can be installed in both new and retrofit situations. Because the hardware requires less space than that needed by conventional HVAC systems, the equipment rooms can be greatly scaled down in size, freeing space for productive use. GHP systems also provide excellent "zone" space conditioning, allowing different parts of your home to be heated or cooled to different temperatures.

Because GHP systems have relatively few moving parts, and because those parts are sheltered inside a building, they are durable and highly reliable. The underground piping often carries warranties of 25–50 years, and the heat pumps often last 20 years or more. Since they usually have no outdoor compressors, GHPs are not susceptible to vandalism. On the other hand, the components in the living space are easily accessible, which increases the convenience factor and helps ensure that the upkeep is done on a timely basis.

Because they have no outside condensing units like air conditioners, there's no concern about noise outside the home. A two-speed GHP system is so quiet inside a house that users do not know it is operating: there are no tell-tale blasts of cold or hot air.

 

Selecting and Installing a Geothermal Heat Pump System

Heating and Cooling Efficiency of Geothermal Heat Pumps

The heating efficiency of ground-source and water-source heat pumps is indicated by their coefficient of performance ( COP ), which is the ratio of heat provided in Btu per Btu of energy input. Their cooling efficiency is indicated by the Energy Efficiency Ratio (EER), which is the ratio of the heat removed (in Btu per hour) to the electricity required (in watts) to run the unit. Look for the ENERGY STAR label, which indicates a heating COP of 2.8 or greater and an EER of 13 or greater.

Manufacturers of high-efficiency geothermal heat pumps voluntarily use the EPA ENERGY STAR label on qualifying equipment and related product literature. If you are purchasing a geothermal heat pump and uncertain whether it meets ENERGY STAR qualifications, ask for an efficiency rating of at least 2.8 COP or 13 EER.

Many geothermal heat pump systems carry the U.S. Department of Energy (DOE) and EPA ENERGY STAR label. ENERGY STAR -labeled equipment can now be financed with special ENERGY STAR loans from banks and other financial institutions. The goal of the loan program is to make ENERGY STAR equipment easier to purchase, so ENERGY STAR loans were created with attractive terms. Some loans have lower interest rates, longer repayment periods, or both. Ask your contractor about ENERGY STAR loans or call the ENERGY STAR toll-free hotline at 1-888- STAR -YES for a list of financing options.

Economics of Geothermal Heat Pumps

Geothermal heat pumps save money in operating and maintenance costs. While the initial purchase price of a residential GHP system is often higher than that of a comparable gas-fired furnace and central air-conditioning system, it is more efficient, thereby saving money every month. For further savings, GHPs equipped with a device called a "desuperheater" can heat the household water. In the summer cooling period, the heat that is taken from the house is used to heat the water for free. In the winter, water heating costs are reduced by about half.

On average, a geothermal heat pump system costs about $2,500 per ton of capacity, or roughly $7,500 for a 3-ton unit (a typical residential size). ). A system using horizontal ground loops will generally cost less than a system with vertical loops. In comparison, other systems would cost about $4,000 with air conditioning.

Although initially more expensive to install than conventional systems, properly sized and installed GHPs deliver more energy per unit consumed than conventional systems.

And since geothermal heat pumps are generally more efficient, they are less expensive to operate and maintain — typical annual energy savings range from 30% to 60%. Depending on factors such as climate, soil conditions, the system features you choose, and available financing and incentives, you may even recoup your initial investment in two to ten years through lower utility bills.

But when included in a mortgage, your GHP will have a positive cash flow from the beginning. For example, say that the extra $3,500 will add $30 per month to each mortgage payment. The energy cost savings will easily exceed that added mortgage amount over the course of each year.

On a retrofit, the GHP's high efficiency typically means much lower utility bills, allowing the investment to be recouped in two to ten years. It may also be possible to include the purchase of a GHP system in an "energy-efficient mortgage" that would cover this and other energy-saving improvements to the home. Banks and mortgage companies can provide more information on these loans.

There may be a number of special financing options and incentives available to help offset the cost of adding a geothermal heat pump (GHP) to your home. These provisions are available from federal, state, and local governments; power providers; and banks or mortgage companies that offer energy-efficient mortgage loans for energy-saving home improvements. Be sure the system you're interested in qualifies for available incentives before you make your final purchase.

To find out more about financing and incentives that are available to you, visit the Database of State Incentives for Renewable Energy (DSIRE) Web site. The site is frequently updated with the latest incentives. You should also check with your electric utility and ask if they offer any rebates, financing, or special electric rate programs.

Evaluating Your Site for a Geothermal Heat Pump

Because shallow ground temperatures are relatively constant throughout the United States , geothermal heat pumps (GHPs) can be effectively used almost anywhere. However, the specific geological, hydrological, and spatial characteristics of your land will help your local system supplier/installer determine the best type of ground loop for your site:

Geology

Factors such as the composition and properties of your soil and rock (which can affect heat transfer rates) require consideration when designing a ground loop. For example, soil with good heat transfer properties requires less piping to gather a certain amount of heat than soil with poor heat transfer properties. The amount of soil available contributes to system design as well — system suppliers in areas with extensive hard rock or soil too shallow to trench may install vertical ground loops instead of horizontal loops.

Hydrology

Ground or surface water availability also plays a part in deciding what type of ground loop to use. Depending on factors such as depth, volume, and water quality, bodies of surface water can be used as a source of water for an open-loop system, or as a repository for coils of piping in a closed-loop system. Ground water can also be used as a source for open-loop systems, provided the water quality is suitable and all ground water discharge regulations are met.

Before you purchase an open-loop system, you will want to be sure your system supplier/installer has fully investigated your site's hydrology, so you can avoid potential problems such as aquifer depletion and groundwater contamination. Antifreeze fluids circulated through closed-loop systems generally pose little to no environmental hazard.

Land Availability

The amount and layout of your land, your landscaping, and the location of underground utilities or sprinkler systems also contribute to your system design. Horizontal ground loops (generally the most economical) are typically used for newly constructed buildings with sufficient land. Vertical installations or more compact horizontal "Slinky™" installations are often used for existing buildings because they minimize the disturbance to the landscape.

Installing Geothermal Heat Pumps

Because of the technical knowledge and equipment needed to properly install the piping, a GHP system installation is not a do-it-yourself project. To find a qualified installer, call your local utility company, the International Ground Source Heat Pump Association or the Geothermal Heat Pump Consortium for their listing of qualified installers in your area. Installers should be certified and experienced. Ask for references, especially for owners of systems that are several years old, and check them.

The ground heat exchanger in a GHP system is made up of a closed or open loop pipe system. Most common is the closed loop, in which high density polyethylene pipe is buried horizontally at 4-6 feet deep or vertically at 100 to 400 feet deep. These pipes are filled with an environmentally friendly antifreeze/water solution that acts as a heat exchanger. In the winter, the fluid in the pipes extracts heat from the earth and carries it into the building. In the summer, the system reverses and takes heat from the building and deposits it to the cooler ground.

The air delivery ductwork distributes the heated or cooled air through the house's duct work, just like conventional systems. The box that contains the indoor coil and fan is sometimes called the air handler because it moves house air through the heat pump for heating or cooling. The air handler contains a large blower and a filter just like conventional air conditioners.

Most geothermal heat pumps are automatically covered under your homeowner's insurance policy. Contact your insurance provider to find out what its policy is. Even if your provider will cover your system, it is best to inform them in writing that you own a new system.


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.

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 on absorption chillers,  call us at: 832-758-0027

www.AbsorptionChillers.comTM

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

 

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