Integration of technologies
The drive to minimise the effects of global warming is tackling three major concerns head on. The first is to reduce the level of carbon dioxide emissions, the second is to improve energy efficiency and the third is to increase the use of renewable energy solutions. A tall order, especially as the attainment of the specified targets in all three areas must be achieved by 2020. Although a clear overall timetable was put in place, decisions regarding the identification and implementation of processes specific to each sector of industry have, understandably, not been uniform.
To avoid the potential pitfalls of what could be called a ‘staggered start’, progress across the board is being achieved by of a mixture of regulation, voluntary agreement, independent initiatives and the evolution of appropriate best practice procedures. One instance of this is the Merton Rule, whereby a single local authority made a policy determination that new non-residential developments had to generate at least 10% of energy needs from low/zero carbon (LZC) solutions.
Subsequently, over 150 further authorities have adopted a similar policy, or are considering doing so. In areas where no formal policy exists, it is quite possible that industry best practice is likely to result in similar targets being voluntarily applied by developers.
This uneven rolling out of the implementation of the European energy policy is not making things simple for the heating and ventilating sector, particularly where existing commercial and public buildings are concerned. The recently introduced Energy Performance Certificate (EPC) and Display Energy Certificate (DEC) are prime examples. One element of both Certificates is a list of changes or improvements that might be made to improve energy performance, but action to implement them is not compulsory. However, as energy using equipment and systems are generally subject to annual inspection or maintenance, questions of component renewal and possibly equipment replacement will inevitably arise, involving a reassessment of energy performance.
Because of the targets relating to increased use of LZC technologies, it will be inevitable that the utilisation of energy sources such as solar thermal solutions heat pumps, combined heat and power (CHP) products and biofuel will be considered. However, reacting to the impetus, indeed urgency, behind the attainment of increased energy efficiency and lower harmful emissions targets, does not imply success at any cost.
The low or zero carbon solutions adopted must be both practical and cost effective and this will raise the question of how they can be integrated with existing conventional products that still have a reasonable service life ahead of them.
A shining example
Solar hot water heating is an increasingly frequently used LZC technology in commercial and public buildings. Solar collectors are used to raise the temperature of the incoming water supply from, typically, 10ºC to say 60ºC. For example, pre-heated water is stored in a cylinder with two indirect coils, the lower coil being served by the solar collector array and the top coil by the heating system boilers, usually via a low loss header. This is to ensure that the boilers do not switch off on over-temperature, as the boiler capacity sized for the building’s space heating requirement is usually much larger in output than the rating of the coil. If there is insufficient solar energy to heat the water to the required 60ºC, the conventional boilers would provide the additional energy. However, during periods of high available solar irradiation, the solar energy absorbed by the collectors and transferred into the hot water can mean that the demand for additional energy from the boilers is limited and can lead to a significant reduction in carbon dioxide emissions. Studies show that approximately 100kg of CO2 per square meter of collector array could be saved each year when compared with burning natural gas.
Going to ground
In a commercial or public building, there may be a low grade heat requirement for under-floor heating, with higher temperatures for radiators and hot water, the total heat load being serviced by a high efficiency condensing boiler using fossil fuel. In such a case, a ground source heat pump could be considered for integration with the existing system. Although an electrical appliance, a ground source heat pump is considered an LZC technology, as energy from the ground is used to initiate and sustain their operation.
The heat pump draws free energy from the ground at around 12ºC (fairly constant throughout the year) via a ground loop and generates heat, by means of a refrigeration cycle, that is used to heat water. A water temperature of around 35ºC is appropriate for an under-floor heating system and at this temperature the heat pump is likely to be operating at maximum efficiency. Although reliant on electricity, using ground source heat pump technology to service the lower heating demand of the under-floor heating system can reduce the heat demand on the conventional boiler. This would save on fossil fuel and this integration of technologies could, on balance, reduce CO2 emissions.
Combined Heat and Power (CHP) technology adds an additional dimension when considering introducing a heat pump into a conventional space and water heating system.
Although a CHP unit may itself rely on fossil fuel for its energy source, the electricity it generates can be used to power a heat pump. If a mini-CHP unit is deployed, the electricity generated would generally be sufficient to drive the heat pump, with any additional CHP output being utilised elsewhere within the building. The heat gain would be used to reduce the demand on the conventional boiler. In this way, the combination of heat pump and CHP technologies, working with an existing condensing boiler serving the heating and hot water system, can make overall energy and significant emission savings.
The right stuff
Biofuel may be another option available when improving existing systems. The term is generally understood to mean ethanol, diesel or other liquid fuels made from crops such as rapeseed, corn and used vegetable oils. After passing through the transesterification process to become either Rapeseed Methyl Ester (RME) or Fatty Acid Methyl Ester (FAME), they are suitable as additive or replacement fuel in oil-fired pressure jet boilers. As well as being carbon neutral, releasing into the atmosphere only the amount of carbon dioxide absorbed during their growth, Biofuels contain no sulphur to damage the atmosphere or the fabric of the boiler. It is possible to install the necessary special flexible oil lines and oil filters and to change fuel injectors and nozzles on certain cast iron pressure jet boilers in existing installations, leading to significant CO2 savings.
Leading the way
There is growing pressure on building owners to play a greater role in the implementation of the European energy policy in relation to existing buildings. Annual inspection of the energy using products and systems within commercial buildings will throw into sharp focus any cost effective measures that could be taken to improve a building’s performance.
Although not yet obligatory, building owners will no doubt conclude that suggested improvements should be implemented. To ensure the most effective specification and integration of LZC technologies for any application, equipment suppliers should be regarded as part of the project team. With a wealth of knowledge and expertise, major solution providers, like Andrews Water Heaters and Potterton Commercial, can provide the technical support needed right from the earliest design stage through to commissioning. In this way, building owners can be sure of a successful LZC technology integration project that will help meet their responsibilities under the critically important European energy policy.