SOLAR POWER


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The direct route to green DC


Roberto Mallozzi, managing director of Gree UK, explains how renewable technologies help drive efficiencies further.


16 T


hese days everyone declares that they want to be green, whether it is to benefit


from the PR of environmental credentials, to save on running cost or from a genuine desire to do the right thing.


The basics steps towards


becoming more energy efficient are well known to most people involved in the industry. At the heart of it lies more energy efficient equipment, moving to heat pump air conditioning and using heat recovery. Especially for businesses, the full cost of installing heat pumps, which are counted as a renewable energy, can be reclaimed against Corporation Tax. The renewable classification comes from the fact that heat pumps typically produce 3.5kW of heat for every 1kW of electricity consumed.


Heat recovery refers to heat that


is generated on the sunny side of the building which can be moved to the shady side, while cooling the warm side in the process – a system known as ‘free heat’. These are all issues I have written about in the past and are well documented.


If you are doing this to save


money, you have to be in it for the long game as installation costs are likely to be higher than conventional alternatives, but the vastly reduced running costs will save money in the long run – as well as the environment. However, to make a real


difference we need to do much more than merely fiting more energy efficient units, although that is obviously a step forward. To make a serious move in the right direction, we need to completely change the way we generate power by moving away from alternating current (AC) to direct current (DC) supply.


We use AC in all our homes and


businesses for largely historical reasons. Back in the 1880s, AC won the ‘war of the currents’ because the preferred method of long- distance electrical transmission has always been overhead power lines. As the length of a transmission line increases, the energy transfer efficiency of the line decreases. The main ways to tackle this are to increase voltage, or to increase wire diameter. At the end of the 19th century, there was


no practical way to change the voltage of DC power, whereas the transformer made that relatively easy for AC power. Consequently, appliances were designed to use AC, but more and more equipment is now more suited to DC, such as LEDs, laptops and other IT equipment. The inverter motors in air conditioning equipment are now universally DC, as this is much more controllable than AC. Many appliances we think of as AC, because we plug them into the mains with a 13 amp plug, are actually DC with a built-in transformer, where power is lost in the transformation. Not only would moving to DC have few downsides, it would also save these power losses.


Since the original ‘war of the


currents’, technology has moved forward. The USSR experimented with it at the end of World War Two, based on technology taken from the Germans after the war, and in 1956 the first practical, working high voltage DC (HVDC) transmission line was constructed between Gotland Island and the Swedish mainland.


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