In many households, the most energy intensive applications are those dealing with the heating of water, refrigeration and air conditioning. These three activities can add considerable expense to the overall cost of a solar power system.
While the heating of water can be taken care of very economically by the implementation of a dedicated flat plate or evacuated tube solar hot water system or heat pump; keeping food and people cool still provide major challenges. Evaporative air-conditioners are energy efficient, but water hogs – and water is a scarce resource in a country such as Australia. Additionally, evaporative air conditioners are useless in humid climates.
But perhaps we’re looking at it all wrongly. For refrigeration and air conditioning, while there are energy efficient appliances available, they require the sun’s rays be converted to electricity and then that electricity is used to power the appliance. In an off-grid solar application, that electricity needs to be stored in a substantial deep cycle battery bank and in a grid connected solar setting, mains power will still need to be accessed.
Electricity also becomes the middleman, and in any power system, the more “middlemen” means the greater loss of energy through various conversions.
What if electricity requirements can be greatly minimized or removed altogether from the equation? Here’s a couple of examples:
Solar powered ice-maker
Developed by students at the San Jose State University, the solar ice maker (pictured above) uses a reflective panel to focus light and heat from the sun onto piping containing a liquid refrigerant. The refrigerant then vaporizes. When the sun goes down, it quickly reverts back to a liquid and its temperature drops dramatically due to pressure differences. Water placed next to the evaporator’s exterior can then be frozen. The San Jose prototype can create around 6 kilograms of ice a day and has no moving parts. The students are currently working on a more compact version of the solar ice-maker.
Solar powered air conditioner
Danish company AC Sun recently unveiled an air-conditioning system based on solar energy that uses requires 10% of the electricity consumption of conventional air-conditioning systems. The reduction in electricity requirements come from the compressor in the system being run by a solar-driven steam engine, whereas conventional air-conditioning systems use an electric motor. While there’s been a few solar powered air conditioners brought to market in recent years, most have been for commercial applications or terribly expensive for domestic applications. AC Sun aims to develop a product that would be price competitive with traditional domestic air conditioning appliances within the next year.
While many of the advances in refrigeration and air conditioning for off-grid applications are in concept stage, there are many companies plowing substantial investment dollars into research and development of such products, so hopefully we can look forward to truly economical and energy sipping appliances in the not too distant future..
