HVAC For Beginners


Combined Heat And Power Production For The Home

CHP is an abbreviation for combined heat and power. This is the latest in heating technology. These systems produce electricity as well as provide heating for the home. Most nation's electrical systems are made up of power plants and the wires that connect them to our homes. This system of wires is referred to as the grid. This system has several disadvantages such as pollution of the air and inefficiency. As electricity flows through a wire, some of it's energy is converted to heat by friction losses. This energy is wasted and accounts for a substantial part of the energy produced. By producing the electricity where it is needed (distributed generation), through CHP systems, those distribution losses are eliminated. Also, the residential systems available in the U.S. use a natural gas powered engine. These engines run cleaner and therefore cause less air pollution than the power plants.

Natural Gas Powered Engines

One type of CHP system uses a natural gas powered generator. This is much like a backup power generator for a home in that it produces electricity by burning natural gas to power a motor that turns a generator. The difference is that the heat produced by the motor is transferred to a coolant that is circulated through a coil. This coil is either installed in a gas furnace or boiler and the heat is transferred to the home's heating system. One such system that is available in the USA and Canada is called ECOPOWER and is from MARATHON ENGINES (marathonengine.com). This unit has an electrical output of 2 to 4.7 kw and a thermal output of about 20000 to 42000 btu/hr. This system is designed for hydronic heating systems and has a large enough heat output to supply most of the heat required for a small home as well as the electricity required. They have built-in software to allow you to manage the heat and electrical production through programming. The systems are currently only available for grid tie use and will not provide electricity when the grid is down during a power outage. They recommend service on the engine after every 4000 hours of operation. YANMAR (yanmar.com) manufactures a system (CP4WE) that produces about 4 kilowatts of electrical power and 34,100 btu/hr of heat for water. The systems can burn either natural gas or propane and are sold through dealers around the world. They have a remote monitoring option and the BOS (black out start) model can provide backup power to the home and replace the traditional standby generator. They have a 10,000 hour scheduled maintenance interval. The ECOWILL from HONDA (world.honda.com) uses an advanced Honda motor and a Vaillant boiler. The ecoPOWER 1.0 system is available worldwide for installation in homes. They have an autonomous operating function for times of power outage but they must be manually started. The DACHS SE from SENERTEC (senertec.de) is available in Europe. It has a larger power output and an integrated boiler for peak heating loads. The KOREMO from AISIN (aisin.com) uses the motor expertise of Toyota for a large electrical power output of 6 kw. In the modulating output mode, the unit is controlled to vary the electrical output based on the demand in the home and the heat is stored in a tank. In the heat control mode, the unit produces maximum heat and excess power is transferred to the grid via net metering.

Stirling Engine CHP Systems

A stirling engine operates using the principle that a heated gas expands and a cooled gas contracts. This principle is used to move pistons to drive a generator. A fuel (natural gas, fuel oil, etc) is burned to heat the gas. The gas is cooled by water in the normal heating system. This can provide space heating as well as hot water for the home. The NAVIEN m-chp unit is a compact wall mounted unit that has a durable stainless steel heat exchanger. The unit has an electrical output of 1 kw and a heat output of 15 - 36 kw. They offer an optional grid independent module. (kdnavien.com) The ECOGEN from Baxi (baxi.co.uk) is not your traditional combi boiler. It can produce 1 kilowatt of electricity as it provides for the home's central heating and domestic hot water production. It is easily installed as it simply needs the normal electrical wires for a traditional boiler. Their innovative THINK CONTROLLER is a programmable control that can also be removed and used as a wall thermostat. The brand is a part of BDR THERMEA. The VITOTWIN 300-W from Viessmann combines a gas-fired combi boiler with a stirling engine in a compact unit. The regular boiler is only used for peak heating while the stirling engine provides electricity constantly and uses the waste heat generated to heat water for domestic hot water as well as central heating. The unit is easily installed as it is very similar to a typical combi boiler. The unit has a durable stainless steel heat exchanger and requires very little maintenance. (viessmann.com) The eVITA system from REMEHA (remeha.com) is made in the Netherlands and is sold in Europe.

Fuel Cell CHP Systems

Other CHP systems using fuel cell technology are in development. Fuel cells have several advantages such as they are silent because they have no moving parts. They also require minimal maintenance and produce negligible pollution. One such unit, the GAMMA PREMIO from BAXI-INNOTECH which is a part of the BAXI GROUP, is in the final test phase. The units are due on the market in 2015. In these units, hydrogen is extracted from natural gas and fed to an anode where the hydrogen atom is split into protons and electrons. The electrons then flow through an electrical circuit to provide power to the home. The protons pass through the membrane and are combined with oxygen at the cathode to produce hot water for heating. (baxi-innotech.de) Another system is available from AISIN for use in homes in Japan. The ENG FARM is commercially available in cooperation with the local gas companies. BLUEGEN (bluegen.info) is a fuel cell system from Australia that is available worldwide. The system can provide up to 36 kilowatt hours of electricity per day as well as 200 liters of hot water. The unit is about the size of a home's washing machine, is virtually silent and has low emissions due to the use of natural gas. The units are primarily used for business places because of their large output. The PURECELL model 5 from CLEAREDGE POWER (clearedgepower.com) can be installed either indoors or outdoors and either in parallel with or off of the electrical grid. Because of their output and cost, they are more suited to larger high end residences.