FREQUENTLY ASKED QUESTIONS

SOLAR

How does it work?
Solar radiation from the sun hits a selective surface (either flat plate or vacuum tube) and this heat is transferred through thermal conduction, radiation and convection to the medium inside the collector. This medium is usually an antifreeze and water mixture and when the solar collectors are hotter than the cylinder, the controller switches on the system's circulating pump. This mixture is then circulated through the collectors and into the hot water tank, heating the cylinder in just the same way as a central heating boiler

What types of solar collectors are there?
There are basically two types of solar collectors, the flat plate collector or a vacuum tube type.
Flat plate collectors are characterised by their excellent cost:benefit ratio and can be installed vertically or horizontally and are best suited to pitched roof installations.
Vacuum tube types offer higher solar yields independent of their location and are primary suited for walls or flat roofs as the individual tubes can be rotated to suit the solar angle needed.
Both systems can also be installed at ground level on angled ‘A’ frame units

Do you need planning permission to put up solar panels?
It is very unlikely, unless you live in a listed building or in a conservation area. It is best to check with your local planning authority just in case.

Will the panels fit on any roof?
It is usual to fit the panels over the existing roof tiles as this is much cheaper, however solar panels can also be integrated into the roof.

How efficient are the panels and how much energy do they generate?
As an approximate rule of thumb one 2.5sq mtr flat panel collector will provide nearly 1000kWh of free energy per year. In the summer months the panels can produce temperatures of well over 100 degrees C, depending on circulation flow rates

Is there a maximum number of panels we can put up?
The number of panels is determined by the storage capacity of your water tank. An approximate value is about 30 to 50 litres capacity per square metre of panel, depending on panel alignment and the collector type.

GSHP 

What is a ground source heating system?
A Ground source heat pump (GSHP) is a low energy system using the near constant temperature of soil or surface water, captured by a network of underground pipes and boosted via a pump and compressor to provide heating to a building ideally through an underfloor system. As an addition if the system flow is reversed, the underground pipe work works as a heat sink providing cooling for the buildings interior.

How do they do that?
The metaphor commonly used to understand GSHP’s is a refrigerator in reverse. A refrigerator removes the heat from its interior into the kitchen via the rear grill whereas a GHSP operates in reverse by absorbing the near constant 10 Deg energy in the earth. The ground is a good energy store as underground temperatures ranging from 7 to 13deg C are relatively even all year round. GSHP systems use a mixture of water and antifreeze circulating through a set of either horizontal or vertical ground collectors to absorb this thermal energy from the earth as it travels around the pipework. Using the refrigeration process, the heat pump removes this stored thermal energy and transfers it to your home, through a heating system.

How much energy is needed to run a GSHP ?
Modern electric heat pumps obtain approximately three quarters of the heat required for heating from the environment the remaining quarter is drawn as electrical power for driving the compressor. The performance factor is a result of the ratio between the transferred heating energy and the energy used (power supplied to the unit) which describes the effectiveness of the heat pump. In general terms 1 unit of electrical input returns 3-4 units of output.

What other types of Heat pumps are there?

Heat pumps can also be operated using the latent heat in water and air.

Water is a good store for solar energy as even on cold days groundwater maintains a constant temperature between 7 and 12 deg The groundwater is extracted via a supply well and transported to the evaporator of the water/water heat pump and returned via a return well.

Outside air offers the least expensive option for exploiting an energy source. Air is supplied via a duct put through the heat pump and returned to the outside ambience. The heat pump also utilises the heated air within the building in conjuction with a controlled ventilation system. These air systems are finding favour in energy efficient houses with low energy demands.

What are the outputs that can be achieved?
Heat pumps can achieve outputs from 4.8kW to 106kW and can even be linked in series to achieve greater outputs for commercial premises.

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