LowHeat takes the heat out of hot water

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Households across Europe could soon be saving both energy and money thanks to the results of the LowHeat project.

Every time we take a shower or bath, wash our clothes or do the dishes, large amounts of valuable energy are literally washed down the drain in the form of warm waste water. Now the LowHeat team have come up with a way of recovering the heat energy from the waste water to supplement the main hot water source.

The system can be easily installed by a professional plumber and is now ready for commercialisation, for use in homes as well as businesses that have a high hot water demand, such as laundrettes, processing plants and hotels. The innovation team behind the LowHeat project believe it could reduce utility bills by up to 10 % in an average household, while in commercial properties the savings could be even higher.

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Waste not, want not

With climate change already making its effects felt around the world, the race is on to clamp down on the big energy wasters and polluters. Often the finger of blame is pointed at energy intensive sectors such as the steel, paper and chemicals industries. However, there are also significant energy efficiency gains to be made in our homes.

Figures from Eurostat, the EU’s statistical information service, reveal that households account for over a quarter of all energy consumption in the EU. Furthermore, although the EU plans to cut its overall energy use by 20 % by 2020, household energy consumption is projected to rise by 20 % over the next 30 years.

In a bid to reduce the impact of our homes on the environment, we are regularly encouraged to do our bit to save energy, for example by switching off lights and appliances when they are not in use.

Turning up the heat on energy wasters

But some sources of energy wastage are hard to spot and even harder to remedy. Take low-grade heat, for instance: large quantities swirl down the drain every day. Low-grade heat is the energy generated from an array of domestic appliances and fittings, such as washing machines, dishwashers, shower units, baths and sinks.

According to the LowHeat partners, there are some 58 million dishwashers, 232 million washing machines and 63 million shower units in the EU alone. It is estimated that 90 % of the energy used by these goes into heating the water, a task which requires approximately 26 500 terajoules of thermal energy. Most of this energy is simply washed down the drain and lost.

Yet few have attempted to use this waste water as an energy source. A previous EU-funded project called WARMIT succeeded in developing a device which could capture the heat from shower waste water. The aim of the LowHeat project was to design a system which could capture the heat from an entire building’s waste water system. The 12 partners from 9 EU member states included small and medium-sized enterprises, research institutions and national heating and plumbing associations.

Introducing the LowHeat system

The LowHeat system is surprisingly simple, comprising a drain device, heat exchanger and wireless control device (optional). As hot waste water is discharged, it passes through the drain device where its temperature is taken. If the water is hotter than 30°C, the system activates a pump which diverts the water through the LowHeat heat exchanger.

Depending upon the type of hot water system within a building, there are two different types of LowHeat heat exchanger. There is an ‘inline’ heat exchanger and a ‘gatlin gun’ heat exchanger and both heat exchangers use heat pipes for the heat exchange process. The ‘gatlin gun’ recovers the heat energy to directly heat a ‘pre-heat’ vessel, whereas the ‘inline’ heat exchanger uses the recovered heat energy to heat the water within the main hot water store.

The LowHeat device is not the first heat exchanger on the market. But what sets it apart from the rest is its ability to capture energy from waste water with temperatures as low as 30°C. Other heat exchangers only work with much higher temperatures and so are not suitable for use in domestic settings, such as in showers and dishwashers, where temperatures tend to be lower.

Another innovation is the system’s wireless control device, which allows households to assess in real time the energy and cost savings being made.

The amount of heat captured varies from one appliance to another: in the case of washing machines, 84 % of available heat energy is recovered, while for sinks and showers the figures are 40 % and 35 % respectively.

Big savings all round

The benefits of the LowHeat system are manifold. In terms of energy savings, the device could help households reduce their energy consumption by 1 000 kWh every year. The project partners have calculated that even with a relatively low market penetration of 6 %, this could reduce energy consumption by 10.1 billion kWh in Europe alone. With energy prices rising, these energy savings will help families reduce their energy bills significantly.

The environment will also benefit greatly from the device, with the project partners estimating that the system could prevent the unnecessary release of up to 4.8 million tonnes of carbon dioxide every year.

According to the project partners, the device will also contribute to the European economy; the system could be worth as much as EUR 1.67 billion in Europe alone, and could create approximately 10 000 jobs.

A winning design

The potential of the system has not gone unnoticed; in 2006 it was highly commended in the UK’s National Efficiency Awards as an ‘example of how good research and development can identify an opportunity for energy and cost saving in a far from obvious application’.

Meanwhile, thanks to endorsements by the plumbing associations involved in the project, the LowHeat system has gained credibility within the industry, and work is now underway to bring the product to market.