Figure 1. Self Sufficient Home with Combined Heat and Power
Combined Heat and Power (CHP)
Engineers combined heat and power (CHP) systems, also known as cogeneration, generate electricity and useful thermal energy in a single, integrated system. CHP is not a technology, but an approach to applying technologies. Heat that is normally wasted in conventional power generation is recovered as useful energy, which avoids the losses that would otherwise be incurred from separate generation of heat and power. While the conventional method of producing usable heat and power separately has a typical combined efficiency of 45 percent, CHP systems can operate at levels as high as 80 percent.
Some micro-CHP technologies use mechanical engines, such as internal combustion engines or Stirling engines. They reach good efficiencies only at larger sizes, so are more suitable. Now, technologies are becoming available to complete the rest of the miniaturized power plant. This is called micro-combined heat and power (CHP). Micro-CHP generates both electricity and heat simultaneously at the size of a home. The heat meets the demand for space heating and hot water, while the electricity provides power for home appliances. (See Figure 1. Above, Self Sufficient Home)
How does it work? Let’s first look at the current status quo. Right now, your boiler burns natural gas at incredibly high temperatures approaching 2,000°C. However, you only need hot water and space heating at ~50°C. At the moment, a gas boiler just lets the heat degrade and cool down, throwing away most of the useful energy content. In comparison, in micro-CHP, that huge temperature difference is used to generate electricity in addition to heat.
Building Energy Codes
Engineers find that strong building energy codes should serve an important role in hazard mitigation strategies for resilient homes. Building codes ensure that new homes meet health and safety requirements, including resilience during and after severe weather events. Energy codes, which set minimum energy efficiency thresholds, are one important aspect of the need for improved building codes overall. (Alternative Energy)
For example, home thermal performance, one factor addressed by building codes, is an important indicator of energy resilience. Increasing the efficiency of a home by improving the building envelope can make a home more comfortable during power outages as efficient buildings stay warm or cool longer than inefficient buildings. Efficient home codes also reduce occupants’ vulnerability to heat waves and cold snaps.
(Figure 2. Mini Home Power Plant)
Efficient Small Generators are Coming
As it turns out, most homes already have half of a miniaturized power plant. Electricity is just a part of our daily energy consumption – we also need heat to keep us warm. We need thermal energy to heat our homes, hot water and food. ( Engineering Energy) And so, in the US, more than 60 million homes are heated by natural gas.
Miniaturized Power Plant
Micro-CHP can attain overall efficiencies of 90% by generating both electricity and heat on demand and at the location where both are needed and valuable. This contrasts with central power plants, which produce electricity at 35% efficiency. At these plants, the waste heat is usually thrown away, since the heat can’t be transported hundreds of miles to where it is needed. The higher efficiency of micro-CHP can help cut homeowners’ energy bills by 30% and reduces their carbon footprint. (See Figure 2. Above, Mini Home Power Plant )
Today’s New Technologies
Today, newer technologies such as fuel cells and thermionic energy converters can reach high efficiencies even at the scale of a single home. This allows micro-CHP to be available to individual consumers and homeowners. ( Layered Composte Heaters)
These new technologies have no moving parts and thus have far lower maintenance requirements and no sound pollution making them more amenable to a residence. Finally, this set-up gives individuals the option of producing power on demand.