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Water special: Turbines turn up the heat

Harnessing wasted energy in water mains could be a simple, cost-effective way to cut fuel bills.

With environmental awareness so high on everyone's agenda, the pressure is on large-scale energy users to find ways to improve efficiency and reduce their power requirements. Consultant Mouchel Parkman has joined forces with a US technology company to offer a solution that makes use of wasted energy by installing "micro-turbines" inside water pipes.

The system is aimed at any industry that relies on water being circulated at pressure, including both clean and wastewater. All water distribution networks tend to have sections – typically on downhill gradients – where pressure needs to be reduced using pressure reducing valves. Micro-turbines installed upstream of these valves can turn this lost energy into electricity.

The solution is being promoted by Rentricity Ltd, a joint venture set up earlier this year between Mouchel Parkman and Rentricity Inc. A trial site has been set up in Stamford, Conneticutt, in the US and UK water companies are already showing considerable interest.

According to Rentricity founder George Taylor, the micro-turbine is designed and configured differently for each site, but 80% of the equipment is available off the shelf. "We look at the site characteristics and see what would fit best," he explains. For example, in wastewater the flow might be very high, but the pressure is low, whereas in water mains you have higher pressure but lower flow."

Output also varies according to the site characteristics, but the turbines could be used to generate between 30kW and 100kW on one site, and up to 1MW if multiple turbines are installed in trunk mains.

Renticity's business model almost eliminates risk for the "host" company. The firm will design and install the turbines itself and then pay a leasing fee while selling the electricity that is generated to National Grid. This arrangement lasts until Rentricity breaks even on the deal, after which there is a revenue share agreement between the company and the host.

The other alternative is for the host company to re-use the electricity itself, bypassing the grid and eliminating the financial risk of energy price fluctuations. The idea is similar to setting up a CHP plant or wind turbine on the site, but with far less visual impact.

"This is all about making companies more efficient," explains Mouchel Parkman's Richard Ingram, who is taking over from Taylor as managing director of the company. "Reducing energy costs is a big driver for everyone. This is energy that’s being lost, and if you can get something back and turn it into energy then it must be a benefit. The biggest benefits will certainly come if you can offset the energy against your own electricity use."

According to Ingham, turbine installation is relatively simple, with the equipment usually buried in underground chambers. If it can be installed when other civils works are under way, then so much the better. He says the front-end cost is usually paid back within three to nine years.

The idea of harnessing hydropower in pipes has been tried before but, says Ingham, turbines are now far more efficient, and Rentricity's approach is different to previous players in this field. "We are not simply selling a product," he says. "We have an interest in the system generating revenue, so we're not going to put it into sites where it's not going to work."

Anglian Water, Northumbrian Water, Severn Trent Water, Yorkshire Water and United Utilities are looking at the idea very closely, and Rentricity is currently working with Thames Water to identify sites for trialling the technology.Surging ahead with new technology

Rentricity came out of Mouchel Parkman's Technology Approval Group (TAG), which was set up as a mechanism for bringing new technology into the water industry.

TAG acts as a sort of "Dragon’s Den" by filtering innovations from technology companies and then sounding out the industry as to which products or services are likely to win favour. Those that get the nod are then taken forward to venture capitalists, or Mouchel Parkman gets involved directly, as it has with Rentricity.

This process enables companies that have developed their products to the prototype stage to secure funding for further development while ensuring that there is clear market demand for those products.

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