Maximising the benefit of solar energy
With the first publication of the CRC Energy Efficiency Scheme league tables due imminently, some companies may need to reconsider their carbon-reduction plans and find ways to further reduce emissions. In addition to complying with the legislation, businesses will also find they save money by becoming more energy efficient. There is a range of hot-water technologies that can help companies to achieve this.
The CRC Energy Efficiency Scheme (previously called the Carbon Reduction Commitment) was introduced in April 2010 and requires around 5000 organisations from both the private and public sector to assess how much energy from all fuel sources they are likely to consume in the forthcoming year. They will then have to purchase a carbon allowance. If the company then exceeds that allowance, it will incur a financial penalty. Companies using less than their allowance will be awarded a bonus.
While the scheme does not start officially until April 2011, companies should have registered and be thinking about ways to reduce their carbon emissions now.
While hot-water generation may not be the biggest contributor of excess carbon emissions, looking for a more energy-efficient solution will certainly ensure reductions can be achieved. Solar-thermal technology is emerging as one of the most popular LZC (low/zero-carbon) technologies, which some organisations have already embraced as a way to lower emissions and cut costs. The popularity of solar could be attributed to the fact it is a relatively simple technology to understand, as well as being a fairly easy solution to integrate with a hot-water system.
It is relatively simple to integrate a solar system in to an existing building, so it can be used in retrofit projects as well as new builds. The Government has outlined plans to scale back on new-build projects, so organisations will need to look for ways to improve existing buildings, and solar can be introduced relatively simply compared to other renewable solutions.
While solar provides a source of renewable energy it will usually only provide a maximum of 25 to 30% of the annual hot-water requirements for commercial buildings. To supplement the hot water generated by solar energy, one of the most effective ways is to use direct gas-fired water heaters. The hot water from solar gain will be used to pre-heat feed water to the gas-fired water-heater installation. Looking at the system as a whole, the larger proportion of a building’s hot-water demand will actually be generated by the more ‘traditional’ method, meaning the selection of this primary source of hot water is equally, if not more, important than the solar proportion.
The use of twin-coil cylinders is common in residential dwellings, with the lower coil being used to transfer the solar gain and the upper coil being supplied with hot water via the central-heating boiler. However, the effect of the solar gain is reduced by the indirect coil from the heating boiler and, furthermore, this indirect method of generating hot water is less efficient than a direct gas-fired water heater.
There is thus clearly a strong argument for using direct gas-fired water heaters with solar thermal systems. Based upon the principles of low storage but fast recovery of hot water, direct gas-fired water heaters use fuel more efficiently than an indirect system. This concept has been utilised for more than 30 years, and most water-heater manufacturers now utilise condensing technologies in the design of their products. The operating efficiencies of modern condensing gas fired water heaters can reach as high as 98%, based on gross CV.
Renewable technologies for generating hot water technologies will clearly play a role in compliance with the CRC Energy Efficiency Scheme, but building owners and occupiers should also remember the importance of the primary equipment. Condensing gas-fired water heaters offer high operating efficiencies and can be integrated with renewable technologies relatively easily, making them an ideal solution for many projects. They can contribute towards reducing carbon emissions reductions, and this is where the technology will play an important role in helping companies to comply with the CRC Energy Efficiency Scheme.
David Pepper is managing director of Lochinvar
