Kyoto – A Perspective (Part 23)

Posted on Fri 05/09/2008 by



Unlike what environmentalists might say, generating electrical power from the heat generated by Sunlight is more complex than you might think. Because of this I’m going to split it into three parts, household generated electrical power, Photovoltaic power, and solar thermal power. As good as it sounds, solar can never be classed as reliable, for the obvious day/night reason, and for those of you living in Northern areas of the US, it is almost out of the question, because there will be times in Winter when snow will cover any solar panels that might rely on the Sun, and the Sun may barely be seen during some times of the year, so even if solar power can be used on a sporadic basis, it can never supply continuous power on a 24 hour basis all year round.

Household Generated.

1. Solar Hot Water.

Solarhart roof mounted hot water system.This photograph shows a roof mounted solar powered hot water system indicative of what you might see on Australian households.

Photograph courtesy of the .

This link takes you to the home page. You’ll see the menu tab beneath the top image, The second one along titled ‘HOME OWNERS’ has a drop down menu with further excellent information.

Australia, you might think, would be the perfect place for the introduction of solar power. In fact, one Company here in Australia has been installing Solar Hot Water Systems in homes for more than 50 years, and they have the system working perfectly.
They have three systems, one with the tank on the roof with the panel, one with just the panel on the roof, and the third with no panel but a thermal system that draws heat from the surrounding air to warm a liquid that converts to a pressurised gas that heats the water. The first two with the panel on the roof pass water over the panel to a trough at the bottom of the panel on the down side of a sloping roof, where the water then is drawn back up as heat naturally rises back to the tank at the top.
The systems save that part of your power bill for hot water. These systems had a boom period in Australia during the Seventies probably due to ‘new fangled’ factor, and those people who installed them at that time have had the long term benefit of the installed systems, provided they have stayed in those homes for all this time. They have come back into vogue recently for all the obvious reasons, and sales are booming so much that other Companies have now moved into supply and installation of them.
Governments have even made it attractive for people to install them by offering rebates, but you can guess what’s happened. The companies gradually raised the price to cover the rebate, so in effect the consumer was still paying the same as he always had, and the Government rebate was going straight to the Company.
The cost averages from $1500 for a small system say for just a 2 person household to $5000 for a family sized system. For an average electric power bill the saving might amount to between a fifth and a quarter of your total bill, so the system could effectively pay for itself over five to six years or so, depending on the government rebate. The possible drawback is what happens during Winter or if you have a period of cloudy days. The system has had a long time now to be perfected and it works quite well, provided you live in a year round sunny place, and not anywhere North of the Mason Dixon line.

2. Solar Generated Power.

My son who was eleven at the time saved some money from his pocket money and bought me a solar powered calculator from Radio Shack for my birthday in 1981. I still have it now and it gets used quite often. It uses the photovoltaic principle in that it works when light shines on the small panel, whereas the solar hot water principle works on dark panels soaking up the heat from the sun and using this heat to warm water for the hot water system.
With the calculator, light from the Sun or any light source generates a tiny voltage which works the calculator, as long as the light is shining on the panel.
This method of Solar generated Power works via the same principle.
Even though with both, you have panels on the roof of your house, the two systems are different.
The inherent problem some of you may be unaware of is that this photovoltaic system produces DC, and all houses are wired for AC, so a way has to be found to convert from the light generated DC. This is done with an inverter.
You cannot have enough panels on your roof to generate enough power to solely run a normal household.
Whereas the hot water system has a panel that is around eight feet by six feet, this photovoltaic system utilises a number of panels of approximately half that size. Each panel is made up of hundreds of the small solar cells, whereas the calculator uses four thumbnail sized cells.
The problem is that the system has to be wired into existing house wiring, connecting it to the main power grid.

The basic system combines an Inverter and the six panels and might be able to produce just over one Killowatt, which could run the hot water, or with no hot water then a refrigerator, some light bulbs and maybe the radio. The oven would be a stretch, as would the cooktop. Heating and airconditioning are out of the question as the average one and a half horsepower reverse cycle airconditioner uses about 1.2 KW. That is why it can only be used to augment the household power from the grid.
The cost starts at around $4000 for the basic outfit, and can go as high as $45,000.

This photograph shows a top of the line solar power array on the roof of a house. This might feasibly generate up to 5.12 KW of power augment the grid supply to an average house.

Photograph courtesy of the .

This link shows the available systems this large Australian Company offers. take further links for each system in those tabs highlighted in blue. All prices are in Australian Dollars.

The larger cost here is the top of the range system, that can produce up to 5KW, which, at a pinch, might be enough to power a house, as long as you can live relatively frugally with regard to electrical power. The idea here is that this is an excellent supplement to your house being connected to the grid, which is a legal requirement, and during sunny periods can feed power back to the grid resulting in a payment from the power authority, which in the long run could prove revenue neutral for household power bills. The inherent problem here is that the house would need to be specifically designed with a large roof area facing North here in Australia, and South in the US, in an area of fairly benign if not hot weather, and at $45,000, it is a commitment to staying in that house for a long period of time, before you recover the cost of the original outlay.

Some Governments subsidise the original cost to a small degree, but the same might also apply here in that the Company will just bump up the price to cover that rebate, so either way, you pay the same. Some governments have also made the attractive offer of paying you for the power the system generates and feeds back into the grid if you are not using it. It sounds puzzling, but if both members of the family work and the children are at school, no one is home. If it’s a bright sunny day, then power is being generated but not used, and what actually happens is that your power meter actually winds backwards as the power is fed back into the grid. Some Governments actually pay double or even triple if this happens. However, the house need to be rewired by an Electrician, and the labour is in addition to the initial outlay, and a special power meter is required to read that ‘backwards’ factor.

So, as attractive as it might seem, the returns are only minimal with an absolute maximum saving on your power bill amounting to not much more than a quarter. In some areas this might in fact be a lot, but you have to weigh up the facts if you are living in Michigan, Texas or Southern California.

The next two pieces I will deal with basically the same principle, only scaled up, the household hot water system being Solar thermal, and the photovoltaic on a large scale.