Electric Power Generation
Electric power generation is an ‘energy intensive operation’ – that is, it takes a lot of energy to make electricity. When electric utility power plants produce electricity from coal or natural gas, the process is only about 30% efficient. Most of the available energy in the source fuel is lost “waste” heat. If BOTH the electricity and heat can be put to use, the process is known as cogeneration or CHP – Combined Heat and Power. With CHP systems, the efficiency can be 80% or more.
A new emerging technology is residential scale CHP units.
How It Works
In order to achieve the best efficiencies, all of the electricity produced and as much of the “waste” heat as possible must be put to use. The electricity will off-set the power purchased from the electric company, and the waste heat will off-set the natural gas used for heating water and space heating (thermal energy). One of the challenges of this technology is matching the electric and thermal demands. The house may not always need electricity and thermal energy at available production capacities at the same time. Thermal energy could be stored, but electricity is typically not stored when using CHP systems, like it may be stored with solar systems. In both cases, storing the energy adds cost to the equipment installation and complexity to the design.
It is also necessary to work with the local electric company on the electrical interconnection with the electric grid. This can sometimes be a challenge as electric grids are designed to flow power into houses, not out of them. There are different ways of making the electrical connections work and there are advantages to a connection that allows the electricity to flow in both directions, called ‘Net Metering’. Net metering is not desired as a money maker for the home owner, but to make the operation of the unit easier. The amount of electricity produced for sale back into the grid should be very small in a well designed system. For larger houses with larger electric base loads it may be very rare, if ever, that power would flow back into the grid.
The Freewatt system from ECR International, is controlled by a call for thermal energy. When the house needs space heat or hot water, the Freewatt unit starts-up and produces both heat and electricity.
2201 Dwyer Ave
Utica, NY 13501
Web site: www.freewatt.com
Source: Text Bob Fegan 5/2009; Freewatt image from their web site 5/2009;