Geowarmth Heat Pumps Solar Biomass Renewable Energy

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Geowarmth: Renewable Energy Solutions

  • Biomass boilers
  • Ground source heat pumps
  • Air source heat pumps
  • Solar thermal
  • Solar PV
  • Underfloor heating & radators

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How a heat pump works

Converting heat from the environment for heating a building
Dimplex house 937x273
The schematic below illustrates the three circuits to consider in a heat pump installation.
The heat source is the blue circuit on the left of the diagram.  The heat source can be air, water or the ground.  Most of the heat absorbed by a heat pump is solar energy rather than geothermal from the centre of the earth.  The heating distribution circuit is the red circuit on the right and represents the hot water flowing around the heating system in the property.  The refrigerant circuit is the green circuit in the middle.  This links the external heat source with the heat distribution system and is contained within the heat pump.
The three circuits are connected within the heat pump by two heat exchangers.  The energy equation on the diagram is important in understanding the reasons for a heat pump's efficiency.  Typically for every unit of electricity input, three to four units of heat are output by the heat pump.  This is also referred to as the co-efficiency or performance or COP.  As an example the seasonal COP of a Nibe F1155-12 ground source heat pump at a flow temperature of 40oC is 4.59 (source MCS database).  Thus in this example for a power input of 1kW, thermal output of 4.59kW is produced.
how a heat pump works
In a typical ground source heat pump installation fluid circulates around the ground in plastic pipes at a lower temperature than the ground, say at 5oC.  This creates a heat gradient and draws heat from the ground into the fluid in the pipe.  The fluid passes through an evaporator (heat exchanger) in the heat pump and the heat extracted from the ground is absorbed by the refrigerant which circulates around the heat pump.  The refrigerant becomes a gas and is compressed in a compressor which causes further heat.  The pressurized refrigerant then passes over another heat exchanger called a condenser where the heat is transferred to the building’s underfloor or radiator pipe work.  Having given up its heat, the refrigerant passes through an expansion valve where its pressure and temperature further reduces returning it to a liquid state to start the cycle again.  The main power consumer in a heat pump is the compressor, but the majority of the energy comes from the environment.

How is a ground source heat pump installed

How we get heat from the ground 

slinky banner 937x273
A ground source heat pump uses (mainly solar) heat stored in the ground.
There are a number of methods of extracting the heat from the ground.  The most common method is horizontal ground loops.  The amount of loops installed is dependent on the ground conditions and the size of heat pump which itself is determined by the heat loss of the property.  Geowarmth undertake all these calculations.
Dimplex heat_pump_house_horizontal_schematic
Horizontal ground loops
Horizontal ground loops consist of polyethylene pipe laid in trenches or a wider excavation.  The depth is typically around 1 metre.  Loops of around 100m in length can be laid in trenches.  Individual trenches usually need to be 2-3 metres apart to get an excavator between them and provide space for temporarily storing the spoil.  Coiled pipe can also be laid in wider tranches per the photograph above.  These are referred to as slinkies.
Where a body of water is available such as a pond, coils of pipe can be laid just off the bottom of the lake. 
Dimplex heat_pump_house_bore_hole_schematicClosed loop boreholes
Bore holes around 150mm wide are drilled at depths of up to 150 metres and loops of pipe inserted in each borehole which is then filled and sealed with a thermally enhanced grout.  This is a more expensive method than horizontal ground collectors but boreholes can be installed where ground space is more limited and they can be put under a building.  The number of boreholes required varies according to the geology of the area, the heating demands of the property and the size of the ground source heat pump.
Dimplex heat_pump_house_open_loop_schematicOpen loop systems
In an open loop (or water to water) ground source heat pump scheme, ground water is abstracted, usually from an aquifer or possibly from a river and passed through the heat pump before being returned to the ground.  A constant supply of water is needed.  This type of ground source heat pump system is more efficient because of the relatively high temperature of ground water, but the installation can be more complex and require regulatory approval.  Open loop ground source heat pump systems are usually confined to larger commercial buildings rather than domestic properties.

How air conditioning works

Converting heat from the air for heating or cooling a building
air conditioning with remote control
 Air conditioning systems can be used to provide space heating, cooling and domestic hot water.

In heating mode, an external heat exchanger or evaporator absorbs heat from the air and transfers it to a refrigerant vapour in the refrigerant circuit. This passes in to a compressor where the vapour pressure is increased which creates an increase in temperature. This higher temperature pressurised refrigerant passes through another heat exchanger or condenser, where it liquefies and transfers heat that can be delivered to the property via the air in the building. The process is also known as a vapour compression cycle.

In cooling mode the process is operated in reverse with heat in the building extracted from the air and disposed of to atmosphere. A variation on this involves heat recovery where the extracted heat from some parts of a building can be used to warm other parts of the property or using a heat pump boiler to provide domestic hot water.

Air conditioning systems are based on heat pump technology with components common to those is a refrigerator.

The efficiency of heat pumps arises from some of the heat or cooling coming from the atmosphere rather than from electricity. There is a ratio of heat delivered to electrical power consumed known as the Coefficient of Performance or COP. In cooling mode this ratio is known as the Energy Efficiency Ratio or EER. Typical values are between 3 and 4 so for every 1kW of electricity input the equivalent of 3 or 4kW of heating or cooling is achieved. Air conditioning heat pumps thus provide a very cost effective way of heating and cooling a building compared with direct electricity and can also compare favourably with other forms of heating.


Replacement air conditioning

Converting older systems to modern air conditioning
replacement air conditioning
 R22 is a hydrochlorofluorocarbon (HCFC) and has been common in air conditioning in the past. R22 gas can no longer be supplied in the UK or used for servicing and maintenance of existing systems. To do so would be illegal. R22 is harmful to the ozone hence it is now banned.

It is therefore necessary to replace existing R22 air conditioning with a more modern alternative such as an inverter controlled system containing the more efficient refrigerant R410A. Geowarmth can offer a rnage of solutions from single room air conditioners to whole building simultaneous heating and cooling systems.

Increases in efficiency of 30-50% should be possible by switching to R410A inverter controlled air conditioning units from old
R22 systems. Higher efficiency means lower electricity consumption and less CO2 emissions.

The cost of change need not be a burden. Various tax incentives are available for replacing old systems such as Enhanced Capital Allowances (ECAs) or Annual Investment Allowances which can allow businesses to write off the cost against tax in year one. In addition finance to businesses is also available.

Please contact us for a bespoke solution

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