Combined Heat and Power (CHP) / Cogeneration

Combined heat and power or CHP, also called cogeneration or distributed generation, is the simultaneous production of two types of energy – heat and electricity – from one fuel source, often natural gas. The ability to create two forms of energy from a single source offers tremendous efficiency and thus both cost savings and environmental benefits. The key components of a combined heat and power system are an internal combustion, reciprocating engine driving an electric generator. The clean natural gas fired engine spins a generator to produce electricity. The natural byproduct of the working engine is heat. The heat is captured and used to supply space heating, heating domestic hot water, laundry hot water or to provide heat for swimming pools and spas. The CHP process is very similar to an automobile, where the engine provides the power to rotate the wheels and the byproduct heat is used to keep the passengers warm in the cabin during the winter months. Benefits of Combined Heat and Power

Because of the high efficiency of the system, combined heat and power provides considerable energy, environmental and economic benefits.

  • Reduce the demand on the utility grid
  • Increase energy efficiency
  • Reduce air pollution
  • Lower greenhouse gas emissions
  • Protect the property against power outages
  • Significantly lowering the utility costs of building operations

Efficiency of CHP Systems Combined heat and power systems use fuel very efficiently. A CHP system provides electricity and heat at a combined efficiency approaching 90%. This is a significant improvement over the combination of the 33% efficient electric utility and a conventional heating boiler with a 60% seasonal efficiency.

CHP Existing Electric Utility Conventional Heating Boiler
Efficiency 90% 33% 60%

Why is there such a big difference in fuel efficiency between the electric utility and a combined heat and power system?

The electric utility and CHP system each produce electricity and heat from one source of fuel. However, the heat produced at the electric utility is not used; it goes into the cooling water or up the smokestack along with greenhouse gases and other pollutants. Approximately two-thirds of the fuel’s energy is wasted. Alternatively, while generating electricity, a properly sized combined heat and power system recovers nearly all of the heat it produces and deploys it on site. In addition, when purchasing power from the electric utility, a separate source of heat, usually a boiler, is required. Despite using an efficient boiler, the total fuel required producing conventional electricity and boiler heat is greater than the amount of fuel required to produce simultaneous energy with a combined heat and power system. This demonstrates why CHP-produced energy is more cost effective than the combined energies from the electric utility and local boilers.

Combined Heat and Power System Candidates

he following qualifying criteria can help determine whether or not your property is a good candidate for a CHP system.

  • The property has more than 120 beds, rooms or units.
  • Natural gas is available on site.
  • Domestic hot water is supplied from a central boiler plant.
  • Space heating is supplied from a central plant with hydronic distribution.

Natural Gas Chiller Cooling SystemsAccend Energy and American DG offer several natural gas chiller system options in the size range from 50 to 1,200 tons. Unlike conventional chiller systems, which use an electric motor to power a compressor driven chiller, a natural gas engine driven chiller uses an internal combustion engine to power a similar compressor in a refrigeration loop. This simple change in how the chiller cooling system is powered creates high efficiency along with heat recovery opportunities for the natural gas engine driven chiller system.

  • Reduces demand on the grid
  • Help alleviate high summer electric costs
  • Prevent seasonal blackouts & electricity shortages

While absorption chiller cooling systems also use natural gas, their efficiency and performance have been disappointing relative to engine driven chiller systems. Although a compressor driven chiller is a very efficient system for cooling a building, using a natural gas engine to drive the compressor makes it even more efficient – 2.5 times more efficient than the most efficient absorption chiller. As a result, a natural gas engine driven chiller cooling system provides greater comfort and savings.

Benefits of Engine Driven Chillers

There are several benefits to implementing natural gas engine driven chillers versus absorption chillers or electric chillers, including efficiency, system footprint and the use of natural gas fuel.

  • High EfficiencyThe primary benefit of a natural gas engine driven chiller is its high efficiency. As an example, a 200-ton system has a COP of 2.6, which is significantly more efficient than most absorption and electric based chillers on the market. And, certainly is much more efficient than your current system.
  • Superior Efficiency due to Recovery CapabilityA natural gas engine driven chiller cooling system provides superior efficiency due to its the heat recovery capability. The heat from the engine, which powers the compressor can be captured through a heat recovery system and then utilized within the building for various applications. The recovered heat can be used to heat domestic hot water, laundry hot water or to provide heat for swimming pools and spas.
  • High EfficiencyThe primary benefit of a natural gas engine driven chiller is its high efficiency. As an example, a 200-ton system has a COP of 2.6, which is significantly more efficient than most absorption and electric based chillers on the market. And, certainly is much more efficient than your current system.
  • Superior Efficiency due to Recovery CapabilityA natural gas engine driven chiller cooling system provides superior efficiency due to its the heat recovery capability. The heat from the engine, which powers the compressor can be captured through a heat recovery system and then utilized within the building for various applications. The recovered heat can be used to heat domestic hot water, laundry hot water or to provide heat for swimming pools and spas.
  • Lower Energy Costs
  • Lower Carbon Emissions
  • Avoidance of on-peak electric demand charges and time of day rates

Taking advantage of the heat recovery capability of a natural gas engine driven chiller provides significant fuel efficiency resulting in lower energy costs, reduced operating costs and reduced carbon emissions. Additional benefits, if converting from an electric chiller, include avoidance of on-peak electric demand charges and time of day rates.

  • Compact SizeAnother benefit of a natural gas engine driven chiller is its compact size. An engine driven chiller is smaller than your absorption system and has the same footprint as your electric chiller. Replacing your existing system won’t require additional square footage.
  • No blackouts and brownouts throughout an emergencyIn addition, a natural gas chiller cooling system can continue to operate during blackouts and brownouts throughout an emergency. Loss of power will not prevent the natural gas chiller from running. Though you still require some electricity to run pumps and fans, the amount of back-up power required is dramatically less than with other cooling systems.
  • Supply ice for rinks or process applicationsFinally, our natural gas chiller cooling systems can also be modified to supply ice for rinks or process applications.