Heat pump, gas or LPG

Cool power

Gas heat pumps can provide both heating and cooling for buildings. They use natural gas, LPG, biogas or other gas to fuel a combustion engine which drives a heat pump cycle. The waste heat from the engine may also be recovered for space heating as well as hot tap water.

Gas heat pumps can reduce fuel consumption and greenhouse gas emissions compared to boilers. Although these systems require fuel to work, they operate as heat pumps. This means that a fraction of the useful heat that the system delivers to the building is extracted from the surrounding environment (usually outdoor air or the ground) and this fraction can be considered renewable.

Gas heat pumps might be advantageous in rural locations where electricity is relatively expensive or not available and gas relatively inexpensive. They are therefore particularly suitable for rural regions that are not connected to the gas grid but do have access to (locally stored) LPG. Because they are driven by a combustion engine, gas heat pumps can provide full heating capacity even with low outside ambient temperatures.

Gas heat pumps offer an alternative to gas boilers and electrically driven heat pumps. Investment costs for gas heat pumps are typically higher than for conventional heat pumps that run on electricity or gas fired boilers. The difference in cost between gas and electricity needs to be large in order to make them financially attractive. Gas heat pump technology has been introduced in Europe only recently and the number of commercial choices and manufacturers is still limited.

General Info

What is it?

A system that extracts heat from the ambient air or the ground to provide heating and cooling.

What are the benefits?

Gas Heat Pumps (GHP) offer a solution for heating and cooling where electricity supply is expensive or unreliable. A gas heat pump is suitable for space heating and cooling and hot tap water, depending on the needs.

Low Carbon: Depending on the system replaced, GHP can reduce GHG emissions substantially compared to fossil-based alternatives. Installations can give carbon reduction relative to a gas boiler up to 30%.

Efficiency: Gas heat pumps can reduce substantially fuel consumption for space heating and hot water production compared to boilers.

How does it work?

Gas heat pumps use natural gas, LPG, or other gas to fuel a combustion engine. The combustion engine drives a heat pump that extracts heat from the ambient air or the ground and delivers it to a heating system of the building. The waste heat from the engine may also be recovered for space heating as well as hot tap water.

Suitability/applicability

Gas fuelled heat pumps might be advantageous in locations where electricity is relatively expensive or not available and natural gas relatively inexpensive. They are therefore particularly suitable for rural regions that are not connected to the gas grid but do have access to (locally stored) LPG.

Gas heat pumps consume fuel to operate. In most cases this is a fossil fuel. However, a fraction of the useful heat that the heat pump delivers to the building may be considered as renewable, as it is extracted from the surrounding environment (usually outdoor air or the ground). In principle gas heat pumps can also be designed to run fully on renewable fuels such as biogas.

As opposed to electrically driven heat pumps, gas heat pumps can provide full heating capacity even with low outside ambient temperatures.

A gas-fired heat pump may also avoid the cost of an electrical service upgrade which is sometimes necessary for an electric heat pump installation.

Office buildings, hotels, hospitals, swimming pools or housing with combined heating, cooling and hot water needs and where the heat recovery from the gas engine can be fully used, are well suited for gas heat pumps.

Modern gas heat pumps provide a relatively good fit with existing heating systems and have become more compact in size.

Detailed Info

Costs, Savings, Earnings

Costs, savings and earnings of gas heat pumps depend on a number of factors:

  • The air conditioning and/or heat distribution system installed.
  • The heating and cooling demand of the building.
  • The climate, country or region (some countries provide subsidies for the use of heat pumps).
  • Fuel and electricity costs: financial savings depend on the energy costs of the system being substituted. Compared to conventional and condensing boilers gas heat pumps can provide substantial fuel savings. The economic savings compared to conventional air conditioning systems depend on the electricity and gas prices.

Environmental Impacts

When properly installed, gas heat pump systems can reduce GHG emissions for space heating and cooling compared to boilers and conventional air conditioning systems. Installations can give carbon reduction relative to a gas boiler up to 30%, and uses refrigerants with low or zero climate change potential.

As opposed to conventional heat pumps running on electricity, gas heat pumps produce local air emissions from fuel combustion.

Gas heat pumps are equipped with a thermal engine and a fluid compressor (like a refrigerator). This type of equipment produces some level of noise and should therefore be placed in a suitable (external) location.

Efficiency

In the discussion of the energy performance of heat pumps the term coefficient of performance (COP) is used instead of efficiency. COP describes the ratio of useful heat that the system is able to ‘pump’ for each unit of input energy. Typical COPs for gas heat pumps are within the range from 1 to 1.6. This means that the heat pump can deliver up to 1.6 kWh of heat for each kWh of fuel input. This is lower than for heat pumps that run on electricity.

Commercial Maturity

Gas heat pumps are a mature technology but have only been available for a couple of years on the European market. In Japan they are much more common. Awareness of gas heat pumps in Europe is low.

Level of Maintenance

MEDIUM: Gas heat pumps may require higher level of maintenance than conventional air conditioning systems and conventional electrically driven heat pumps because they include a combustion engine.

Compared to boilers or conventional electric heat pumps fewer qualified maintenance and repair personnel are available for gas heat pumps in the EU.

Technical Details

Gas heat pumps use natural gas, LPG, or other gas to fuel a combustion engine. The combustion engine produces the mechanical power that drives the compressor of a heat pump.

A heat pump works like refrigerators in reverse. Systems are able to extract heat from a low temperature source in their surrounding environment (external ambient air or from the ground) and transfer it to a higher temperature medium (hot water or the internal space of a building). This is achieved by using a fluid that evaporates at low temperatures. When it evaporates, the fluid absorbs heat from the environment. The heat pump then compresses the vapour, increasing the temperature and the pressure. The liquid is then pumped along a condenser where it releases (inside the building) the heat that had previously absorbed from the environment. This cycle continues as long as heating is required.

In gas engine-driven heat pumps the waste heat from the combustion engine may also be recovered for space heating as well as for hot tap water.

Reversible heat pumps can do this process in reverse (by means of a reversing valve), extracting heat from the internal space of the building and releasing it back to the environment.

The process is depicted in the figure below.


Source: www.proheatpump.eu

Regional variations

In northern latitudes heat pumps are used primarily for space heating purposes. As they are reversible systems, they are also used for cooling purposes in warmer climates, extracting heat from the building and delivering it to the external ambient air or the ground.

Trade associations

European Heat Pump Association

www.ehpa.org

Association of the European Heating Industry

www.ehi.eu