Welcome to the solar panels century

Often described as the sleeping giant of renewable energy, solar heating technologies have been a woefully overlooked option to massively increase the renewable contribution to energy supply. However, with superb efficiency and a wide range of applications, the technologies that make up the solar thermal sector are indeed making inroads to the market.

With a surface temperature of some 6000°C, the colossal fusion reactor that is our sun radiates truly prodigious amounts of energy. Indeed, so much power is emitted that, residing some 93 million miles away, the upper atmosphere of the Earth continuously receives an average of around 1.4 kW/m².

After passing through the atmosphere, the light reaching the surface of the Earth is mostly split between the visible and infrared spectrum, but of the energy which remains, the atmosphere, oceans and land masses absorb approximately 3850 ZJ (x1021) per annum. By way of perspective, total global energy consumption is currently estimated at around 500 EJ (x1018).

It is therefore somewhat surprising that use of direct solar radiation has not focused more closely on solar thermal technology. In terms of investment, significantly larger sums worldwide are ploughed into solar PV technology. This is partly due to the relative investment requirements necessary to initiate production. The comparatively simple technologies and materials required in solar thermal systems have allowed small and medium enterprises to dominate the sector. Conversely, the high investment costs associated with solar PV manufacturing have largely precluded smaller players from entering the market and left the field dominated by major industrial operations such as Sharp or BP.

Nonetheless, the relative levels of R&D and manufacturing investment between PV and solar thermal become even more surprising when considered in terms of their relative energy efficiencies. Experimental PV systems are currently yielding maximum efficiencies of over 30%, while the most efficient commercially available solar thermal technologies are yielding efficiencies of approximately 70% under optimum conditions for load, positioning, temperature and such like. It is no surprise that solar thermal is frequently referred to as ‘the sleeping giant of renewables’ by its proponents.

There is no dispute that solar thermal has a vast potential to improve the renewable energy contribution of many nations, but this goal remains some distance away. Part of the issue is the widespread perception that solar thermal technologies are only suitable for those regions with high-intensity insolation. This is a misconception. For instance, as Kevin Brennan, head of sustainability for Velux, says: ‘Currently only 0.004% of the UK’s housing stock has solar water heating, yet over 76% of homes in this country could successfully make use of this technology.’ Brennan continues: ‘While installing solar thermal in all homes across the UK could prove a challenging task, a commitment from housebuilders to incorporate this technology into all of their new builds could still have a significant impact on reducing the UK’s carbon emissions. Within 30 years, the new homes being built today by housebuilders will be approximately 30% of the entire housing stock, so even small gains today will be significant gains in 30 years time.’

Even so, while it may not have achieved even close to the penetration level its efficiency, simplicity and cost-effectiveness may warrant, there is cause for optimism.

A major boost for the industry is the projected development of new, cheaper, materials. While rising prices in copper have seen a number of manufacturers switching to cheaper and lighter aluminium as an absorber surface, the use of alternatives such as polymers is also attracting a great deal of interest.

Although current generation plastics tend to become brittle under high levels of sun exposure and also tend to suffer in an overheat scenario, there has been progress and such developments are expected to dramatically reduce the cost of solar thermal systems in the next few years.

In addition, a number of large buildings material and equipment companies such as Vaillant, and Buderus, part of Bosch Thermotechnology Ltd, have introduced solar thermal packages of late. There is growing interest among developers too, with a number of recent acquisitions by larger renewables players, now ready to offer a full range of technologies. For example, Renewable Energy Systems Ltd (RES) announced the acquisition of solar thermal company Future Heating Ltd this year.

Policy drivers related to climate change are also having an impact, with the forthcoming EU Renewable Energy Directive raising the profile of solar thermal among commercial, industrial and commercial operations.

Perhaps most fundamental to the growth of solar thermal installation, the issues of energy security of supply and the spiralling costs of fossil fuels are certain to improve the economics of alternatives.

However, it should also be remembered that solar heating and cooling technology is nothing new. In the 1870s, French solar pioneer Auguste Mouchout demonstrated its potential by making ice using a solar steam engine attached to a refrigeration compressor. Despite this remarkable success, his project was abandoned shortly thereafter as falling coal prices rendered it uneconomic.

Times have certainly changed, and once again it seems that the conditions are right for solar thermal to come out from the shade.

Source - Renewable energy world