Carnot cycle heat pump heating a house
![carnot cycle heat pump heating a house carnot cycle heat pump heating a house](https://online.fliphtml5.com/vvba/asbu/files/large/101.jpg)
With improved standards of construction, the point at which modern housing needs heating will be somewhat lower than this (probably nearer to an outdoor temperature of 11C).
![carnot cycle heat pump heating a house carnot cycle heat pump heating a house](https://dandelionenergy.com/wp-content/uploads/2019/10/sld1-720x400.png)
This happens to be just below the average outdoor dry bulb temperature in southern England over the ‘heating season’ for housing, assuming that houses require some form of heating as outdoor temperatures fall below 15.5C (the base temperature used in the degree-day energy estimation method). These are based on measurements being made at standard external temperatures of 7C. In the case of a standalone heat pump system (known as a ‘monovalent’ system) that is being used to heat domestic hot water, this requires the use of a direct electric heater for brief periods to bring the stored water to an adequate temperature for legionella protection.ĪSHPs are recognised in the England and Wales Building Regulations Approved Document Part L4 as being appropriate for heating buildings when they have a COP of not less than 2.2 when being used for space heating, and not less than 2.0 when also being used for heating domestic hot water. Clearly, this is a temperature below that needed for the safe operation of domestic hot water where, to reduce risk from legionella, any hot water storage needs to be regularly heated to 60C3. The majority of heat pumps currently in the marketplace are best suited for use with low temperature systems, such as underfloor heating at 30-45C, fan coils at 35-55C, and radiators sized to operate at 45-55C. The efficiency, in terms of coefficient of performance (COP) (see CIBSE Journal October 2011, p51, for definition), is variable depending on the operating conditions and the refrigerant used, but can range from under 1 (when external temperatures are very low and the unit produces almost the same heat energy as the electricity it consumes) to COPs of 3 and above under spring/ autumn conditions when supplying low- temperature heating systems. Based on data collected in real applications by the Energy Savings Trust, properly installed and operated systems can provide typical savings2 in a three-bedroom semi-detached house of £380 per year (or 4,440 kg CO2 equivalent) when replacing electric heating, and £80 (or 810 kg CO2 equivalent) per year when supplanting oil heating (and, with the better performing systems, this can rise to £610 and £310, respectively, and can even save £130 when compared to gas).įigure 1: Monovalent heat pump installation sized at 100% of heating design load requires supplementary heating when outdoor temperatures are below design conditions. Unlike other ‘renewable’ technologies, the application of ASHPs will still use electricity or gas to fuel them, so may not be seen as the purest form of renewable heat but, with appropriate application, they can effectively draw on the practically inexhaustible and freely available source of heat stored in the air.Īppropriate use of an electrically powered heat pump can be cheaper than using an oil-fuelled or condensing-gas boiler, as well as reducing operational carbon emissions. This article considers some of the current requirements and trends in their application. So they are increasingly likely to come under consideration as a means of providing heating and hot water. Although they do not currently attract any Renewable Heat Incentive (RHI) payments, the recent changes to the permitted development rights in England for ASHPs have eased the planning requirements for domestic installations (and some currently attract a one-off Renewable Heat Premium Payment1). We will start from ideal heat engine modeled by Carnot cycle.If appropriately applied, the air source heat pump (ASHP) can be an effective means of providing heating energy for buildings in temperate climates, such as that of the UK. And in order to achieve good COP the much lower output temperature would be needed. If work required to compress the gas was included into the computation the COP would be visible. If the COP did not decrease with increasing temperature difference, it would be possible to construct a perpetual motion machine of the second kind. The bigger is the difference between input and output temperature -> the more work must the heat pump do to transfer the heat. This ratio is called Coefficient of Performance or COP. One joule of work executed by the heat pump can transfer several joules of heat - for example 4 joules (it is the reason why the heat pump is efficient "source" of thermal energy).
![carnot cycle heat pump heating a house carnot cycle heat pump heating a house](https://www.cibsejournal.com/wp-content/themes/cibsejournal/images/2012-01/images/1.png)
It should not generate heat (ideally) it should only force the heat to move. Heat pump should transfer heat from outside into the house.