Renewable energy can be generated through lakes and rivers

  • 10 Jan 2014

For properties that are located near rivers or lakes, water source heat pumps should certainly be considered if affordable energy sourcing and sustainability are desired.
A water source system is usually a preferred option for heat pumps, wherever possible, because it offers the most efficient method of heat extraction for a heat pump, in comparison to other methods.

Water is efficient at retaining heat and, in many cases, this ranges between 7 and 12O°C, depending on the time of year. Anyone considering this system of heat pumps needs a nearby water source with a sufficient yield. Extracting water from a natural source, when using over 20m3 per day, also requires an extraction licence from the Environment Agency. There are two main methods of heat extraction for water source heat pumps – open loop systems use ground water from an aquifier and well and closed loop systems use a water and antifreeze mixture in a ground loop. In most cases, collected water passes through a heat exchanger, which removes some of its heat and the chilled water is then returned back to the source through a second well. 

As energy prices increase and the Renewable Heat Incentive has its planned introduction this spring, water source heat pumps are becoming aneven more attractive option. The owners of a large historic former mill in Bedale have recently undertaken a major refurbishment which includes having a water source heat pump system installed, which generates its energy from a nearby river. Previously the owners were heating their substantial six bedroom home via an oil fired boiler, costing over £5,000 every year.

Water is efficient at retaining heat and, in many cases, this ranges between 7 and 12O°C, depending on the time of year

Danfoss approved heat pump installer AV Commercial designed a system which included two ground source heat pumps fitted in an open loop method to extract water from Bedale Beck, which at its closest point was less than 4m from the property.

The system draws water into a well and then pumps it into a plant room 150ft from the river, where it enters a 1,100L settling tank with reverse washable filter and two heat exchangers which deliver heat from river water to the brine loop. The house also features a 400L hot water cylinder and a 200L buffer tank. The homeowners acquired
an Abstraction Licence from the Environment Agency, as the system uses more than 20m3 of water. The system is expected to save the homeowners around 50% on energy bills and will pay back in less than five years. The two, 12kW heat pumps supply the property with space heating through underfloor heating and oversized radiators in some areas of the property. The heat pump also supplies the home’s hot water needs.

Water source heat pumps are proving an increasingly popular option, not only for domestic properties, but for commercial projects too. Manvers Waterfront Boat Club, a watersports club in South Yorkshire,  provides all the heat for its café facilities, changing rooms and showers through a water source heat pump system. The boat club reviewed the various energy sources available to them and heat pumps proved to be much more affordable to run. On this project, the boat club had a closed loop system installed where pipes were laid in a 12m depth of water, with divers placing the 4 x 200m ground loops deep on the bed of the lake, which were then secured at regular intervals. Loops from the lake are then laid in a 130m trench from the lake to the building entrance.

A heat pump was selected with a large capacity of 26kW. The project also featured a 400L buffer tank to enable adequate space heating and a hot water tank.

Using a water source system means there is much less need for ground works than with a ground source system, which can make it more cost-effective and quicker to install

The design of the heat pump also means it provides high annual efficiency, which minimises energy consumption and can meet the requirements of the canoe club, which currently has 500 members and attracts over 6,000 visitors per year.

Water source heat pump systems are gaining popularity due to them being the most efficient type available. River water has a relatively high temperature, which means that it optimises the running of the heat pump. Using a water source system also means there is much less need for ground works than with a ground source system, which can make it more cost-effective and quicker to install.

As pressure increases on developers and architects to specify renewable heat systems for new homes and buyers continue to demand affordable running costs, the use of water source heat pumps will continue to grow. For anyone living near a lake or river, the reasons for making use of the natural resources near your home or building for energy generation have never been stronger.

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