At the fraction of the running cost of a conventional gas boiler, an Open-loop ground source heat pump installation could:
> Meet all your heating needs
> Meet all your water needs (subject to analysis and suitable filtration)
> Provide an additional grey water supply
The Earth continually absorbs heat from the sun and stores it in the ground, below the Earths surface. At depths below 1 metre, the ground temperature is consistently between 8°C and 14°C. A ground source heat pump is designed to use this constantly renewed energy to supply domestic heating and hot water.
Open-loop systems are the most efficient ground source heat pump option. They extract heat from ground water before returning the same water to the ground, where it immediately begins to regain heat from the earth. The abstraction and recharge (return) of water should be separated by as great a distance as possible within the site constraints to minimise the impacts of potential temperature pollution. The implications of mixing warmer and cooler bodies can encompass environmental concerns but would also reduce the temperature differential over time and thereby reduce the efficiency of the system.
This type of system will only work in areas where there is sufficient ground water available. H.D. Services Ltd. specialise in the installation of open-loop systems throughout South-East England, specifically in areas underlain by the chalk aquifer. To request a feasibility study, please click here.
With an Open-Loop installation, a water supply borehole would be drilled and water at a temperature of around 11°C pumped into the building, where flow could be diverted to feed both a potable (drinkable) water supply and an open-loop heat pump. The heat pump extracts heat from the water and uses it to raise the temperature of water being circulated throughout the house. There are usually two separate water circuits, one for space heating up to 55 °C and another for domestic hot water up to 65°C.
Cooled water at around 6°C is directed from the heat pump back into the ground, where the ground temperature warms the water back up. A harvesting tank can be installed to store the discharge from the heat pump, thereby providing a water supply for garden irrigation or other ‘grey-water’ use. Unlike rain water harvesting tanks that are only replenished when it rains, a heat pump harvesting tank is replenished whenever the heat pump is in operation. If the harvesting tank is buried in the ground, the water starts to reclaim heat immediately.
Subject to analyses, water extracted from the borehole can be filtered for domestic consumption before being returned to the ground via a harvesting tank. Water from the harvesting tank can be used for garden irrigation and other ‘grey-water’ uses. This harvesting tank is replenished whenever the heat pump is in operation.
An abstraction licence is not required from the Environment Agency provided the abstraction rate does not exceed 20,000 litres per day. To date, none of our open-loop installations have required an abstraction licence.
A large open loop system design may require an abstraction licence from the Environment Agency even if the water is returned to the source.
If you require further information regarding abstraction licences, please contact us or visit the Environment Agency website.