Tri-Generation - Electricity - Heat - and Refrigeration
Absorption chillers provide an economic and environmental alternative to conventional refrigeration. Combining high efficiency, low emission power generation equipment with absorption chillers allows for maximum total fuel efficiency, elimination of HCFC/CFC refrigerants and reduced overall air emissions.

Combining a cogeneration plant with an absorption refrigeration system allows utilization of seasonal excess heat for cooling. The hot water from the cooling circuit of the cogeneration plant serves as drive energy for the absorption chiller. The hot exhaust gas from the gas engine can also be used as an energy source for steam generation, which can then be utilized as an energy source for a highly efficient, double-effect steam chiller.

Up to 80% of the thermal output of the cogeneration plant is thereby converted to chilled water. In this way, the year-round capacity utilization and the overall efficiency of the cogeneration plant can be increased significantly.

The diagram (see Image 1) illustrates the simplified operation of a typical tri-generation power plant for refrigeration, electricity, and hot water. This technology utilizes waste heat through a peak load boiler to absorption and compression refrigeration equipment, while generating electricity for on-site consumption.

The actual Situation without CHP and / or Tri-Generation
Most recently the U.S. Government, through its Department of Energy and the National Renewable Energy Laboratory, conducted a research project to analyze current energy inefficiencies and to define effective ways to reduce energy losses. The blue chart (see Image 2) shows the actual situation.

Two-thirds of our natural resources that are burned to produce electricity (mostly coal and natural gas) are lost as heat to the environment. Today’s traditional power plants are only 33% efficient. Most electricity consumers are not aware about the fact that the generation and distribution of electricity through the national grid is notoriously inefficient. Conventional power plants emit the heat created as a by-product of electricity generation into the environment through cooling towers, flue gas, or by other means. Also in most engines and standard diesel & gas generator sets,  more than half of the available energy is lost as excess heat.

Already in 1978, the U.S. Congress recognized that efficiency at central power plants had stagnated and sought to encourage improved efficiency with the Public Utility Regulatory Policies Act (PURPA), which encouraged utilities to buy power from decentralized and private energy producers. However, the bill left implementation and enforcement up to individual States, resulting in little or nothing being done in many parts of the country. Relatively low prices for raw materials like coal, fossil fuel, and natural gas created further complacency.

Tri-gen CHP systems can be employed over a wide range of sizes, applications, fuels and technologies. The heat produced during power generation is recovered, usually in a heat recovery boiler and can be used to raise steam for a number of industrial processes, to provide hot water for space heating, or as mentioned above with appropriate equipment installed, cooling and refrigeration.

Because CHP systems make extensive use of the heat produced during the electricity generation process, they can achieve overall efficiencies in excess of 90% at the point of use. CHP is a form of a decentralized energy technology. CHP systems are typically installed onsite, supplying customers with heat, refrigeration and power directly at the point of use, therefore helping avoid the significant losses which occur in transmitting electricity from large centralized plants to the customer.

Installing CHP is a way of making savings when compared to traditional systems. Due to the high fuel efficiency of CHP plants, the carbon dioxide emissions per kWh of electricity or heat generated are relatively low. A well-designed and operated CHP plant will therefore improve energy efficiency and significantly reduce carbon dioxide emissions.

CHP is an application of technologies to meet end-user needs for heating and/or cooling energy, and mechanical and/or electrical power. Recent technology developments have "enabled" new CHP system configurations that make a wider range of applications cost-effective. New generations of renewable energy systems, and advanced reciprocating engines are the result of intensive research, development, and demonstration by government and industry. Advanced materials and computer-aided design techniques have dramatically increased equipment efficiency and reliability while reducing costs and emissions of pollutants.