Heat Pumps

Why Use Heat Pumps?

A heat pump is one of the most effective ways to heat or cool a building using renewable energy. Unlike many other forms of renewable energy that depend on  the sun shining or the wind blowing the energy for the heat pump is always available. Heat is widely available in the ground, air and water around your house. These natural sources of heat are constantly replenished by the sun, wind and rain. A heat pump system will harness these free and renewable energy sources for heating your house and supplying hot water at a very low cost.

Heat pumps are very economical, for every 1kW of electricity used to power the heat pump, 3 to 6 kW of heat is generated. This is called a Coefficient of Performance (COP).

Annual Costs of Heating Systems Independent studies state that  heat pumps are cheaper and more efficient than fuel oil, gas and wood pellet heating. However attention to detail on the installation is critical to success.

Benefits of using Heat pumps

  • Unlimited heat available in ground or air.
  • Economical – provides operating cost savings of 30% to 60%.
  • Comfortable – maintains an even temperature and humidity level throughout your home.
  • Safe – no open flames, no fumes and no soot.
  • Flexible – one single unit handles heating, cooling and hot water.
  • Dependable – contains few moving parts and requires little or no maintenance.
  • Value – increase the value of your home along with decreasing your energy running bill.
  • Efficiency - as much as five times as efficient as conventional systems.
  • Low running costs – e.g. heat 2,500 sq ft house for as little as £400 per year. EPC rating of B1.
  • Environmentally friendly – our systems emit no carbon dioxide, carbon monoxide or other greenhouse gases.
  • Units available for all sizes of dwellings – new and existing.
  • Improve Building Energy Rating. (EPC).

 

The heat pump has the ability to extract heat from one source (i.e. ground or air) and discharge it into another (i.e. underfloor or radiators).

How a Heat Pump works

The  heat  pump  works  on  the  same characteristics as a standard domestic fridge but, instead of cooling, it heats. Heating   and   cooling   are   achieved by   moving   a   refrigerant   through various   indoor   and   outdoor   coils and components. A compressor, condenser, expansion valve and evaporator  are  used  to  change  the state of refrigerant from a liquid to a hot gas and from a gas to a cold liquid.

Main Stages

  • The refrigerant (liquid state) passes through the outdoor evaporator coils at a low temperature.
  • The water/antifreeze from the ground loop enters the unit and heat is transferred from this water/antifreeze to the refrigerant.
  • The refrigerant begins to boil and changes to a vapour.
  • The vapour  is  pressurised  by the compressor where the temperature is increased to over 100 degrees.
  • The vapour then enters the condenser heat exchanger and the heat is given up to the coils. At this point, the heat is transferred to the  buildings  heating,  and hot water systems. As it passes through the coils, it cools and turns back into a liquid.
  • The refrigerant which is now cooled liquid at high pressure passes through an expansion valve, which reduces the pressure so that the liquid can re-enter the evaporator and begin the cycle again heat from one source (i.e. ground or air) and discharge it into another (i.e. underfloor or radiators).

Heat Pump efficiency

Heat pump efficiency (COP) is obtained by comparing how much energy it consumes in order to complete the heating and cooling cycle. Coefficient of performance (COP) defined as: ‘The ratio of heat delivered by the heat pump and the electricity supplied to the compressor’

Electricity is needed to power the heat pump, but for every unit of electricity used, it will generate 3 to 6 units of useful heat, largely dependant on output temperature.

COP = Kilowatts Output / Kilowatt Input

11.6 kW / 2.8 kW = 4.14 (Waterfurance NSKW12 at W0/W35)