Renewables and low carbon working together
Published: 03 June, 2015
Combining low carbon technologies with renewable energy technologies and having an overarching single integrated control system maximises run cost savings and reduces payback times, explain Stuart Lawrie and Tony Amis of GI Energy.
The rewards for combining different renewable energy technologies with an integrated control system are remarkable when it comes to installing heating and cooling systems in buildings. Carbon savings can be maximised and payback times significantly reduced if the synergies between different low-carbon and renewable technologies are exploited to produce a system that delivers more than the sum of its parts.
Even for major projects, payback times can be as little as six or seven years. Eligible installations will continue to attract the government’s Feed In Tariff and Renewable Heat Incentive for 20 years, bringing in cash flow.
Forward-thinking companies are installing fully integrated renewable energy heating and cooling systems in order to meet the carbon savings dictated by planning regulations, which are particularly strict in London.
At one major landmark project currently in the GI Energy portfolio, an integrated renewable-energy installation is expected to provide over 30% of the site’s energy requirements from combining low-carbon and renewable systems.
Not only will it save £100 000 a year on running costs and 530 t of carbon emissions a year, it will also be eligible for almost £100 000 a year in RHI payments — with a payback of less than 10 years.
The project exemplifies how different renewable technologies can deliver even more carbon savings if combined in the right way with one control system.
Combined heat and power (CHP) plants, for instance, are far more energy efficient than conventional power stations (which on average convert only a third of the energy it burns into electricity). CHP converts up to 80% of the energy burnt into useful heat and electricity. However, their main drawback is they produce a mixture of heat and electricity all the time. Although the proportion of each can be varied, some heat is inevitably produced in hot weather.
The remaining 20% of the energy burnt in CHP plants is lost forever, with 15% escaping straight up the flue, while another 5% radiates as heat from the casing of the plant.
Capturing and storing waste heat until it is needed can significantly increase the efficiency of the system. This can be done by combining CHP with a ground-source heat pump system.
Running a CHP system with a GSHP system which can utilise the extra heat and use it or deliver it, via a network of underground pipes, to the ground is highly efficient. Once underground, the heat can be stored until cooler weather returns, when it can be extracted by the GSHP system to heat the building.
GSHP systems then recycling heat between a building and the ground, significantly enhancing the efficiency of the GSHP and CHP systems, as well as reducing CO2 emissions and running costs.
We have developed the idea of using surplus/waste heat generated from other sources, such as heat that is rejected from refrigeration units in supermarkets. We are now seeing increases of 20 to 30% on heating and cooling efficiencies compared to those obtained by running a stand-alone GSHP system — efficiencies that are already greater than a building which uses conventional gas central heating or electrical air conditioning.
To maximise carbon savings further, the heat pumps can be powered by electricity produced by solar PV panels. In addition, solar-thermal panels can be used to warm a hot-water supply — with surplus heat being stored or used via the GSHP system.
Altogether the return on investment for integrating low-carbon and renewable heating and cooling solutions is excellent. Savings in running costs, combined with the Renewable Heat Incentive helps to enhance paybacks to around eight years.
The key is to have a truly integrated system managed by a single control strategy.
It is not enough to install a variety of different renewable technologies and hope for the best. Optimum results will only be achieved if the system is designed and run as a whole with one control system overseeing it all.
Intelligent monitoring and control systems can be designed and installed that make decisions about when to shift the balance between the different technologies — depending on both internal and external building conditions, including when top-up/back-up heating and cooling provided by traditional boilers or air conditioning are needed (normally as a last resort).
Integrated systems should be designed, sized, installed and then managed through a long-term monitoring regime by experts who truly understand how the different low-carbon and renewable-energy technologies can work together. We devise the optimum solution, regardless of whether the installation is going into a new build or whether it is being retrofitted into an existing building which may have some renewable energy systems already in place.
Retrofit projects, in the same way as new-build projects, can achieve significant ongoing carbon and energy-cost savings, provided the mix of technologies selected is correct and installed with one intelligent control system that can continually optimise the operation of the complete energy system.
An intelligent control system can be set to optimise either carbon savings or energy consumption, depending upon a company’s priorities. For most the energy saving is seen as more important, although we are seeing an increase in targeting carbon savings.
With the Kyoto agreement deadline of 2020 looming close, many companies are looking for ways to cut carbon emissions. Integrated renewable heating and cooling systems offer them many opportunities to do just that.
Stuart Lawrie is chief executive of GI Energy, and Tony Amis is business development director.
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