Potential for savings through the use of regenerative energies in air-conditioning and ventilation technology
Building services engineering in general as well as air-conditioning and ventilation technology in particular have a crucial role to play in implementing the climate protection targets proposed both by the German Federal Government and at European level. Alongside the use of energy-efficient equipment and installation technology, the use of regenerative technologies assumes great importance in all this. With just the technologies available today for the use of renewable energies in air-conditioning and ventilation systems, a contribution of some nine per cent towards the attainment of the Federal German Government's climate protection targets for 2020 can be achieved. Solar-driven air-conditioning, geothermal energy, free cooling and indirect evaporative cooling are at the heart of regenerative technologies for ventilation and air-conditioning. Heat recovery, too, is seen by many experts as a form of regenerative energy, and there are a good many reasons for this view. ISH, the world's leading trade fair for the bathroom experience, building services, energy and air-conditioning technologies and renewable energies will be presenting the latest state-of-the art air-conditioning, cooling and ventilation technology under the Aircontec brand from 10 to 14 March 2009 in Frankfurt am Main.
Heat recovery in domestic dwellings and in public and commercial buildings
The 'low energy house' is setting today's energy standards for new builds and is also setting targets in renovation work. Domestic ventilation with heat recovery offers significant energy-saving potential here. Current estimates suggest that less than five per cent of existing domestic dwellings are equipped with heat-recovery units. Raising this proportion to 30 per cent would be a simple way to achieve savings in primary energy consumption of almost 22,000 GWh. This represents a saving of 6.5 million tonnes of CO2. A similar picture is to be found for the use of heat recovery in public and commercial buildings, where it is assumed that currently only about one in every two air-conditioning and ventilation systems sold is equipped with heat recovery. If, as from today, every newly installed central air-conditioning and ventilation system were equipped with an efficient heat-recovery unit, then we could save as much as an additional 400,000 tonnes of CO2. By the year 2020 this would amount to a CO2 saving of six million tonnes. Added to this, depending on the use made of these installations, they repay their initial costs in from one to five years.
In the field of air-conditioning and ventilation technology, solar energy can be used for thermal cooling of water or for sorption systems. Both processes are ideally suited to situations where air is to be cooled and, where necessary, dehumidified. In principle, both these systems mostly offer, at one and the same time, very efficient heat recovery and, where necessary, de-humidification, a fact which makes it possible to operate the system in winter in such a way as to optimise energy consumption. Solar-thermal cold water systems have the advantage that familiar and commercially available components can be used throughout the entire system. In recent times numerous solar-driven air-conditioning systems have been installed in public and commercial buildings in Germany. Spreading these systems even more widely opens up enormous potential for savings as becomes clear from the following figures: if the proportion of solar-driven water-based air-conditioning systems in new installations were raised to 30 per cent, on an annual basis, that would amount to savings in primary energy of some 75 GWh. This corresponds to CO2 savings of more than 16,000 tonnes. Similar figures obtain in the case of solar-driven sorption units: if the proportion of sorption-based air-conditioning units in new builds were increased to 30 per cent in the market as a whole (including cooling) then primary energy savings of approximately 100 GWh could be achieved. This represents an annual reduction in CO2 of 21,200 tonnes. That means that a saving of around 500,000 tonnes of CO2 would be possible by the year 2020.
Using geo-thermal energy
Geothermal energy just below the surface is particularly suited for use in air-conditioning and ventilation systems. The temperature of the undisturbed ground beneath the surface to a depth of approx. 100 metres is 8 to 12°C. This reservoir of energy can be tapped using a variety of different systems. The ground water can be used directly; ground heat-exchangers can be installed, as can ground collectors or probes as well as ground-air heat exchangers. With careful planning, installation and maintenance, these systems can significantly reduce energy requirements for ventilation and pre-cooling. There has also been opportunity for a further spread of such systems in terms of domestic ventilation. In many instances larger ventilation units, too, have been connected to ground-air heat exchangers. The use of geothermal energy in air-conditioning and ventilation engineering opens up notable potential for energy savings: a figure of 30 per cent geothermal re-cooling in newly installed air-conditioning systems would enable savings in primary energy usage of 32 GWh. Greater use, too, of free cooling and indirect evaporative cooling can contribute, in significant measure, to the urgently required reduction in primary energy consumption.
With innovative technologies for energy efficiency, expert engineering strategies for operational use and modern developments in cooling technology in the air-conditioning and ventilation sector all, therefore, make an essential contribution to the reduction in primary energy consumption, the reduction of CO2 emissions and the conservation of resources. For environmental and political reasons, economically more favourable, more publicly effective and regulatory conditions for the use of regenerative energies in air-conditioning and ventilation technology must be promoted so as to ensure that around 30 per cent of the market is developed every year using these measures.