Like SESSA, Google is also getting behind the push for home and building-scale consumer renewable energy generation with the recent launch of an initiative which assists American consumers to assess the rooftop solar potential of their homes, a clear sign that rooftop renewables can now be considered mainstream. Google Sunroof allows one to drill down to a particular building or house and factors in local solar irradiation data and rooftop orientation in order to arrive at a projected generation potential.
Whilst the service is still new and is only available in certain regions in the US, Google plans to roll it out to others too. This bodes well for a country like South Africa which offers even greater opportunities for rooftop solar than the US.
In South Africa, inland solar radiation averages around 20 mega-joules per square meter per day (MJ/m2) and is slightly lower on the coast (Cape Town through to Richards Bay) at around 18 MJ/m2 per day. As long as the solar installation faces north and is not shaded, it is easy to determine the potential for rooftop solar.
The simple SESSA guideline for calculating Eskom power replacement with solar thermal power for water heating is to determine the amount of hot water used in the home for washing. It takes 1 kWh to heat 36 litres of water to 40 °C which is the temperature that it feels comfortable to wash at. Since a typical shower consumes 16 litres of water per minute, one simply adds up the minutes that all the occupants in a home spend in the shower daily and then multiplies this figure by 16 litres and then divides this by 36 to get an estimate of the energy consumed by showering (in kWh) per day.
Choosing a solar water heater by obtaining its deemed kWh output per day, enables the consumer to determine the level of electrical and financial savings they can achieve against the electricity currently consumed through water heating, whether it be 60% or 100% or anywhere between as the target saving.
In much the same way that a photovoltaic panel of 280 watt output over 6 hours will generate approximately 1.68kWh, a solar water heater with its solar collector will save a kWh figure. The major difference between the technologies is that a solar water heater stores the energy in hot water (think of it as a thermal battery), while solar photovoltaics requires a battery to store electrical energy.
In a similar manner to Google Sunroof, the SESSA guideline provided above enables the homeowner in SA to estimate kWh savings through solar water heating to a fair degree of accuracy. SESSA believes that solar water heating can replace 12% or more of Eskom’s total daily output, as well as having a positive effect on Eskom's carbon emissions profile.
As electricity prices continue to rise, embracing solar thermal technologies will become increasingly attractive, and with the kWh savings of a solar water heater and knowledge of the cost per kWh, the consumer can easily determine their return on investment (ROI) on the cost, including the payback period in months and years.
Despite South Africa not having a single energy efficient incentive program in existence in August 2015, (extraordinary in times of load shedding and power shortages) SESSA believes it is almost inevitable that by 2030, most homes will have embraced consumer renewables, whether it be solar water heating, solar photovoltaics or both. The investment is simply going to get more and more attractive.
Initiatives like Google's are a significant step towards empowering individuals to take control of their energy future. SESSA advises consumers to adopt rooftop renewables as a high priority, being a sound investment for their future, as well as the future of the planet through reducing carbon emissions.