Photo of the house showing some of the solar panels and solar hot water system
I was happy to read that Zaytuna Farm had installed an off grid solar power system for their electrical requirements — “Advanced Solar, and independence, at PRI’s Zaytuna Farm”. However, upon reading the comments relating to this, I could see that there was quite a lot of misunderstanding and misinformation relating to solar power. This inspired me to write a series of articles covering pretty much all things solar power, what it’s all about and how it works.
My solar power knowledge is comprehensive and growing all the time. This is because I live in the Macedon Ranges in Victoria in a house I built myself which has an off grid solar power system. Having a mild dose of technical geekiness (although this is not necessarily a prerequisite!), I obtained and installed all of the components myself . This system now provides all of the electrical needs of the house. I received no government subsidies or RECs (Renewable Energy Certificates) in the process (because it was cheaper not too) and maintained electrical compliance and Australian standards relating to the power system.
In order to understand a solar power system, you need to understand the term “watt”. Wikipedia defines the term “watt” as one joule per second and that it measures the rate of energy conversion. That’s not a particularly useful definition for easy understanding. In explaining what a watt is, I find that it’s useful to think about light bulbs. We all know what they are, but they each use different amounts of electricity. You may have heard about incandescent 100 watt light bulbs which used to be a bit of a standard in Australia, but fortunately are no longer sold here. You may have also heard about 50 watt halogen down lights, or 15 watt fluorescent light bulbs. The watt rating describes how much electrical energy will be used by this appliance if on for an hour. What it doesn’t tell you is how efficient the appliance is, or, taking the light bulbs as examples, how much light they put out. It is only describing the amount of energy used and nothing else.
References to watts are usually expressed as: number and w. eg. 100w means 100 watts.
Watts can also be expressed in thousands of watts or kW. eg. 1kW is 1,000 watts.
Remember that watts are usually measured over a period of an hour, like a car’s speedometer does for kilometres. Watts are usually expressed as so many watts per hour. eg. 1kW/h is actually measuring 1,000 watts of energy generated or consumed in 1 hour.
Solar power systems come in two forms:
- Off grid (or standalone); and
- Grid tied
The off-grid (or standalone) solar power system is like the one installed at Zaytuna Farm in that it literally is not connected to the electricity grid which supplies power to the majority of households. If the electricity grid fails, then Zaytuna Farm will still have electrical power. However, if the people at Zaytuna Farm don’t manage their power usage against their power generation then they will have no power. Off grid solar power systems are generally very expensive because you have to incorporate a facility in your system to store electrical energy (usually batteries) as well as having a place to store the batteries which are quite heavy and a charge controller to ensure that your system doesn’t abuse the batteries.
Grid tied solar power systems are the usual system that you see in urban areas as they are cheaper. The systems are connected to the electricity grid. If for any reason the grid fails, the system automatically shuts down regardless of whether it could feed energy into the electricity grid. The result of this is that the grid connected house will also not have power, even if they are generating solar electricity. The reason for this is that it is possible that the energy generated from the solar power system could potentially electrocute a linesman working on repairing the fault in the grid system. In addition, when the solar power system is not generating any electricity, then electricity is drawn from the grid like any other household.
Either system can be installed anywhere. Having an off grid solar power system is not just for those that live in rural areas. I am unaware of any legislation in Australia that states that a house must be connected to the electricity grid. There is no reason that you could not install an off grid solar power system in a 120 year old terrace house in Fitzroy in Victoria.
I chose to install an off grid system because when I built my own house, I tried make the house have as small a footprint on the environment as possible whilst being as temperate as possible, wanting to make it pleasant and easy to live in. This also meant that I needed to understand about my electricity usage in order to determine if off grid solar was suitable for my needs.
The sad thing is that new houses in Australia are designed and built to be mechanically heated and cooled. They are also sited to face the street which may or may not be appropriate from a solar point of view. Also the materials and the usage of those materials that are favoured by Australian culture reflect ease of construction and form over functionality. This means that from an energy perspective they are expensive to live in, but quick to build and, some may argue, also cheap to build.
In Australia, electricity is predominantly generated using brown and black coal. The electricity generators work by burning the coal to heat water. When the water boils under pressure, steam is produced which then turns a turbine which generates the electricity. What you may also be unaware of is that quite a lot of oil is also used in the process, generally in the mining and transport of the coal.
Burning that coal results in quite a lot of carbon dioxide being emitted. Where I live in Victoria, the coal is known as brown coal due to its higher moisture content. This means that the burning of brown coal is an even less efficient process and generates more carbon dioxide for the electricity produced. It’s not dissimilar from burning wet unseasoned timber as it takes much longer to start burning and it produces less heat whilst burning as energy is consumed in the process of drying the timber out during the actual burning process.
There are a lot of different figures available on the average daily household consumption of electricity in Australia. However, they all seem to be in the range of 15kW/h to 20kW/h per day. For the best case scenario at 15kW/h per day, that’s the equivalent of having 150 x 100w incandescent light bulbs on for 1 hour every day. In comparison, that translates to 1,000 x 15w fluorescent light bulbs. You can see why they stopped the sale of incandescent light bulbs!
On my off grid solar power system I use about 3kW/h per day. Your bill from your electricity supplier will normally tell you how much your average electricity usage is per day in kW/h.
So, what uses up a lot of electricity in a house? A simple rule of thumb is that any appliance that either heats or cools uses a lot electricity. There are some exceptions to this such as plasma televisions which can use as much electricity as a refrigerator.
Examples of items that use electricity to cool are:
- Deep freezers
- Air conditioners
Examples of items that use electricity to heat are:
- Heaters (radiators or fan heaters)
- Hair dryers or straighteners
- Incandescent bulbs – these are very inefficient for lighting as they generate a lot of heat as well as light.
- Halogen down lights – these are also inefficient for lighting as they generate heat as well as light.
Now this doesn’t mean that you should go feral and not use an iron on your clothes — it also depends on how long the appliance is on. You might only use an iron for a few minutes, however, that second fridge in the garage may be using more power than you think as it is on all day, every day. Or, that fan heater that you leave running over night in winter might be the cause of a sudden increase in your electricity bill.
In my next article I will describe how solar power systems work.
As part of the article series, I’m happy to take questions via the comments facility and incorporate the answers into following articles. As a guideline though I will only respond to questions where the products are commercially available and it is feasible for a small scale renewable energy system which can be installed and maintained by someone of reasonable competence. For example: there was a comment relating to the use of solar powered pumping, water tanks and a small hydro generator between two tanks. I would respond to this as it is certainly possible. However, if you are asking me about capturing solar thermal energy and storing it in molten salt to be able to generate power at a later date through a steam turbine, I’d have to say that this is only applicable to large scale systems and beyond the average installer.
As for feeding garbage to a Mr Fusion generator attached to a DeLorean motor vehicle so that you can power a flux capacitor so that you can travel back in time, forget it!
Click here to continue to Part II.