Solar Power

All Kins Domains will be equipped with solar array systems based on thin-film solar panels, non-grid connected. Before I go into detail of the system we will be using, it is worth a quick diversion into solar power systems and terminology.

Solar Panels

There are three forms of solar power generation on the market. Mono-crystalline, Poly-crystalline and Thin-film. All of these are manfactured into panels.

Poly-crystalline panels are the least efficient of the crystalline variety, but also the ones nearly all solar supplier will attempt to sell you. They were developed in the early 1980's by Solarex, to address the issues of high energy production cost and low packing density prevalent with the then existing circular "ingot" based Mono-crystalline cells.

Poly crystalline cells are a square "ingot" based technology, that omit the second refinement step necessary to form mono crystalline cells. The material is less pure, and more susceptible to current and voltage drop with increasing cell temperature. They have a characteristic speckled blue appearance, displaying the large grain structure and a titanium anti reflective coating.

Poly-crystalline cells are very susceptible to temperature, so they need to be de-rated by at least 20% at cell operating levels of 50 degrees celcius, which is typical under field conditions. Panels are manufactured by joining cells together (typically 36).

Mono-crystalline panels date back to the 1950's and early space exploration, which was their main use.They have basically changed very little since that time. The production of Mono-crystalline solar cells is a tedious, convoluted and high energy process.

For both Poly-christalline and mono-chrystalline cells the time and energy taken to produce cells in this manner is not consistant with the ethos of environmental sustainability... which is what the proponents of such products claim to be the main benefit of using them. It takes many years before a nett energy gain occurs from their use.

The best technology for solar panels are the new generation thin-film solar panels which are based on Copper , Indium and Selenium (CIS). These panels are solderless (giving the benefit of less lead in the environment) and are a one piece construction (like the cells in solar calculators and watches). They have excellent temperature stability, and broad band radiation response (meaning they work well when partially in the shade and in lower lighting levels).

The factories that produce thin-film solar panels can be built at a small fraction of the cost of factories producing 50 year old crystalline types, and consume comparatively miniscule amounts of raw materials and energy.

Thin film panels offer the ultimate in sustainable, mass production potential and this will prove critical to stabilise the environment. If you unwittingly purchase crystalline solar panels, sadly, you are merely grafting wings onto a brick!

Why not grid connected?

In Australia there is a strong push towards grid-connected solar systems (where the national power grid is available). Unfortunately this push is mainly politically motivated, to entice the unwitting consumer to invest in public infrastructure, with minimal benefit to themselves.

Is only appropriate if you wish to invest in serious "energy farming", and are prepared to install solar energy capacity way above your own daily average requirements.

In a grid-connected system the solar grid feed inverter synchronizes to, and runs in parallel with the grid, feeding excess production into the grid, and drawing from it as required depending on the availability of solar energy and the electrical load presented by appliances at any given time.

Simple grid feed systems do not provide any electrical isolation or protection from mains borne disturbances and outages as they are in "parallel" with the mains supply. Neither can they guarantee supply, because they have no battery back up, and, in my opinion, if you are spending thousands of dollars on an advanced power system, it should be failsafe, and guarantee stable supply.

Utility companies favour grid feed because:

• It gives them access to renewable energy generating capacity without any capital outlay of their own.
• Enables their marketing gurus and spin doctors to tell consumers how clean and green they are.
• To on sell this energy to others at a premium rate.

Utilities also do not favour batteries in solar power systems because it gives the consumer independence and choice of supply. They often denigrate batteries, claiming they are expensive, maintenance prone and inefficient. However, in well crafted systems this is not the case at all, on the contrary they enable quality, stable power to be realised.

A solar power system

All solar power systems consist of essentially four key components. The solar array, the storage system, the regulator and the inverter.

The solar array is simply a collection of solar panels connected together in "parallel" to provide electricity from the sun. Parallel means that the panels operate at the same voltage (typically either 12V or 24V) but their current generating capacity is added together. Current is the thing needed to charge the storage system, the more current, the faster the storage system charges up for your use.

The storage system is normally batteries, but you can also do tricky things like to us the solar energy to pump water into a tank (thus you are storing the energy for later use in the water being higher than it was previously).

If you leave the photovoltaic panel connected to a battery, the battery will slowly charge up. If you are putting in more energy than you are taking out, then the battery will eventually become fully charged. If this continues, the battery will become overcharged and be damaged by corrosion of it's plates and loss of electrolyte.

Enter the solar regulator. This device monitors and controls the charging of the battery array. Once fully charged, it then disconnects the solar array so that your batteries are not damaged. Some regulators can then direct the power to a secondary source (such as a water pump as in the case above).

Lastly an inverter is required to convert the direct current (DC) solar electricity stored in the battery array into alternating current (AC) which is something "normal" electrical appliances expect (specifically 220V AC in Australia). This output is then fed into the electrical wiring in the house. 

Do not use inverter's with square wave or modified square waveform output's or unpredictable performance will be obtained with certain appliances. Some sales people describe these inferior units as "modified sine wave", Pseudo sine wave", or "quasi sine wave" so as to confuse the unwary. To avoid damage and degraded performance from appliances, insist on true sine wave.