Combined Heat and Power - CHP as a single standalone up to 200 KW or networked as two or more into resilient electric Micro Grids is a very cost effective system for on site power generation, wether a remote site diesel micro grid or natural gas fueled micro grid in an urban setting. The investment for this technology can be readily recovered in about five years or even less in most applications.
For each kilowatt of electricity produced by a conventional reciprocating power generator wether diesel or natural gas, requires upwards of 3 kilowats of energy that must be purchased. This implies 60 - 70 % of this purchased energy is rejected as heat into the atmosphere, most thru the exhaust, and the engine coolant, and about 10% from the engine block and generator windings.
CHP technology, utilizing air to water and water to water heat exchangers will recover a little less than 2 kilowatts of rejected thermal energy from the engine to produce the this single kilowatt of electricity. Thereby increasing overall energy efficiency from a conventional 30% to 80% or more. See folling links:
CHP networked into Micro Grid:
CHP system efficiencies can be futher optimized when two or more CHP units are networked as a resilent thermo electric micro grid, such as two or three buildings within a close configuration. These micro grids offer in particular resiliency to main electric grid failures, and as all interconnections are buried, will offer even further benefits of resilience to climate weather extremes, such as winter ice storms to summer fire storms that can have devasting effect on conventional power grids.
Generator 'Spinning Reserve' Optimization for Thermal and Electric Energies:
During off peak electric load periods, a CHP generator may only need to provide 30% to 50% of peak electric loads; the difference between these two is referred to as 'spinning generator reserve', and can be very cost effectively redirected to other devices to further enhance overall energy efficiencies. Thermal energy will be captured regardless from the engine, however, if spinning reserve electrical energy could be directed to heat pumps, thermal efficiencies can be substantially increased in comparison to conventional fossil fuelled boilers. As example, air to water heat pumps with an average annual COP of 2.5 will yield efficiencies of about 150% or a 75% improvement over basic conventional boilers, at a marginal added cost, commercial cold climate heat pumps with COP of 2.5 at -25C will further improve improve efficiencies in cold climate enviornoments.
Electric efficiency can be improved with spinning reserves by directing electric energy to a battery pack, as this stored electric energy can be redirected to meet periodic surge demand or for peak demand periods. Size of battery pack can determine size of CHP, and this will often correlate with amount of imported fuel for the CHP in order to meet those often short time period peak power requirements, by reducing this amount.
RENEWABLE ENERGY Integration
CHP can be also readily integrated with an already installed solar electic, solar thermal or geothermal as example. A containerized CHP system can have solar electric or thermal panels preinstalled on the container. These systems can be rapidly deployed when delivered to site, as remainder of system is already integrated with the CHP, either electric and or thermal inside the container. Further the solar systems provide a visible architectural and environmental statement, otherwise the install can be just another freshly painter container replacing the old one that house the power system.
Solar thermal and electric have been integrated with air to water heat pumps as customized systems in Europe for many years see link as follows, and use this basic model to integrate with CHP technology:
Further, as the CHP container already has the solar electric or thermal controls as a prepackaged integration, the renewable energy component could be scalable as ground mount or roof top after as an example, as an optional project. This visible component is likely to attract much more attention to key decision makers once the benefits of the CHP system as a standalone is verifed, and spur funding for enlarged renewable component. In principle after the five or so years, savings from the CHP can be readily redirected to the renewable component.
Renewable energy technology face critical problems of energy storage, as do CHP systems when off peak for electric and or thermal loads. It is for this reason battery systems can be readily incorporated for the electric energy side of the CHP with solar electric. Reciprocaing engine electric power generation often faces what's called 'spinning reserve' at off peak electric load time, as the momentum of the reciprocating engine mechanical components need to move at a certain rpm to maintain a fixed voltage or Hertz, or most electronic type items will not funtion properly, among many other electrically driven items.
This spinning reserve electric energy can vary to 80% of generator peak capacity, as 80% being the optimal performnce for the electric generator, engine and best fuel consumption. If generator is at 30% capacity, it has a spinning reserve of 50% of the nominal genertor capacity, this surplus energy could be converted to charge the same battery pack as the solar electic system. This will certainly add cost, but the efficiency would improve substantially, especially on a diesel grid where 30 to 35 cents per KWh are the lowest rates as example.
HEAT PUMP EFFICIENCY
As thermal energy recovered from the CHP during winter is directed largely to the hydonic space heat load, spinning reserve electricity, especially on coldest winter nights, could also be directed to a combination of air to water and or water to water heat pumps. Each KW electric will be capable of a COP of 2 to 4 times. So as example, even if only 10 KW is collected in a multi array solar installation in the northern latitudes on an average winter day, this energy in a water to water heat pump can be tripled or quadrupled to 30 to 40 KW from night time spinning reserve of the CHP, as base electric loads are at lowest, yet this spare spinning reserve energy can be direced to power heat pumps to meet the higher night time thermal loads. Air to water heat pumps are not as efficient at colder ambient temperatures, but units are now availble with COP of 2.5 at -25C, however at additional cost over conventional air to water heat pumps.
Most efficient heat pump is a water to water, where the supply temperature from the CHP thermal recovery can be maintained at a consistent 35 to 40C, this will yield a COP of 4 or greater. Thermal efficiency of the supplied fuel will be well in excess of 100% with addition of this equipment added to a conventional CHP. Add a solar thermal array and the thermal efficiency of this system can be in excess of 150%, well suited for regions with high annual frost days.
Further, a more expensive battery storage for electrical surplus from the CHP or solar electric array can readily be integrated, and in a remote site could meet base electric needs during the summer months, thereby minimizing the use of imported fuel for the CHP.
CHP technology can be readily integrated with conventional hydronic heating. Hydronic coil loops can be adapted to air blown duct based systems as well.
Most suitable applications for quickest investment are loactions with high winter space heat requirements, and basic dometic hot water needs. However if this thermal energy can be directed to a commerical application such as a car wash, laudromat or recreationalal hot tub, swimming pool, then the system utilization is increased over the summer months which will reduce the time frame for investment recovery.