Solar Cogeneration and Net Metering Systems
A cogeneration plant often referred to as a combined heat and power plant is tasked with producing electricity and thermal energy in the form of heat or steam, or useful mechanical work, such as shaft power, from the same fuel source.
Micro-CHP engine systems are currently based on several different technologies: Internal combustion engines, Stirling engines, Fuel cell, Microturbines, Steam engine/Steam motor using either water or organic chemicals such as refrigerants.
Micro combined heat and power or mCHP applies to single or multi-family homes or small office buildings in the range of up to 50 kW. Local generation has the potential for a higher efficiency than traditional grid-level generators since it lacks the 8-10% energy losses from transporting electricity over long distances as well as 10–15% energy losses from heat transfer in district heating networks due to the difference between the thermal energy carrier – hot water – and the colder external environment.
Most Systems use natural gas as the primary energy source and emit carbon dioxide. A micro-CHP system usually contains a small fuel cell or a heat engine as a prime mover used to rotate a generator which provides electric power, while simultaneously utilizing the waste heat from the prime mover for a building’s heating, ventilation, and air conditioning. A micro-CHP generator delivers electricity as the by-product or may generate electricity with heat as the by-product.
Micro-CHP systems have been facilitated by recent technological developments of small heat engines
|Electrical efficiency at rated power||34%||40%||42.5%||45%|
|CHP energy efficiency||80%||85%||87.5%||90%|
|Transient response (10%–90% rated power)||5 min||4 min||3 min||2 min|
|Start-up time from 20 °C ambient temperature||60 min||45 min||30 min||20 min|
|Degradation with cycling||< 2%/1000 h||0.7%/1000 h||0.5%/1000 h||0.3%/1000 h|
|Operating lifetime||6,000 h||30,000 h||40,000 h||60,000 h|
CPVT Concentrated photovoltaics and thermal also called CHAPS combined heat and power solar, is a cogeneration technology used in concentrated photovoltaics that produce electricity and heat in the same module. The heat may be employed in district and water heating, air conditioning, process heat or desalination.
Net metering micro-CHP systems achieve much of their savings by the value of electrical energy which is replaced by auto produced electricity. A generate-and-resell model supports this as home-generated power exceeding the in-home needs is sold back to the electrical utility. This system is efficient because the energy used is distributed and used instantaneously over the electric grid.
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