Parts of a power line

Diagram of a typical solar lighting kit

Diagram of a typical solar lighting kit

There are two approaches to seting up a solar lighting kit which can both be used at the same time or seprately. In the past, when inverters were less efficient and more expensive most solar lighting was 12v DC or low voltage. Current advances in inverter technology and mass production mean more solar lighting kits are basd around an inverter and use lower cost mains voltage lamps and components.

DC based solar lighting kits need thicker cables, special DC switches and new wiring. An AC solar lighting kit can use readily available switches and existing cabling. If you just want to run a couple of DC lamps in a garden shed/workshop then you're not going to have much problem but anything more that and you should start thinking about it a bit more. The diagram illustrates the DC Solar lighting connected directly to the Steca PR3030 solar charge controller. The PR303 controller has an output designed for a DC solar lighting circuit (or a similar low current load) and has a usefull push button switch and a sensor that will turn the output off if the battery voltage low (AKA LVD or low voltage disconnect) The switch is solid state which means it doesn't have any contacts which means it won't suffer from any arching problems commonly associated with low voltage high current circuits. It isn't for an inverter and must only be used for lower power devices!

The higher the voltage the less loss there is over longer lengths of wire. This means you can use thinner wire without loosing too much voltage. If is for that reason that the cables carrying mains electricity run at hundreds of thousand of volts. Transmitting 12 Volts over thin cables looses lots of voltage. The last thing you want to do is start wasting all that precious solar power that's been converted into electricity and stored in your solar battery.

12V or 24V DC has the advantage that it's relatively safe unlike 230V AC which is most definitely not. When choosing or designing your solar lighting kit make sure you consider above points. Think long term because once you've started using solar lighting with perhaps one or two bulbs we bet you a pound to a pinch of salt you'll want to illuminate the entire neighbourhood in the near future!

What if hot air could become electricity? That is the goal of clean technology startup company, Alphabet Energy, based in California. It has a new so-called thermoelectric material which it says can turn waste heat – such as that from car exhausts and industry – into usable electric power more cheaply and efficiently than ever before, saving both money and the environment. 

The company, which was founded in 2009 and has raised over $30m in investment, released its first product which uses the material last October. The E1 thermoelectric generator, which comes in a shipping container, is designed to help make remote-location mining and oil and gas extraction operations more efficient by capturing waste heat from the exhaust of the small, diesel-fuelled power plants they use. Fuel consumption and greenhouse emissions for a one-megawatt power plant can be cut by up to 2.5% – the equivalent of saving 52,500 litres of fuel a year. There has never been a larger thermoelectric generator, Scullin says, adding it is more than 20 times bigger than existing ones. He won’t disclose sales figures but says it is getting “very good early traction” and he expects to see sales ramp up further in 2015, with improvements continuing to be made to the core technology.

The company is prototyping other products, with the possibility that some could be ready to launch in 2015. “The E1 is simply our market entry point,” says Scullin. The company is working on more industrial applications – such as a generator to attach to a factory furnace – and is also working with car manufacturers to harness heat from vehicle exhaust. “From huge mining trucks all the way down to passenger cars we are actively pursuing products,” says Scullin. There are no thermoelectric generators on car exhausts, although a few prototypes have been built and tested in the past, he says.

Thermoelectric materials can generate electricity from heat because electrons flow from warmer areas to cooler ones. But only a few known materials have the rare combination of properties that make them effective. They have to be good electrical conductors but also poor thermal conductors so the temperature difference across the material doesn’t disappear too quickly. Commercial manufacture is difficult because the materials can be rare, expensive, toxic or complex to synthesise. Thus far they have only really found niche applications. For example, their reliability – they are solid materials that don’t require maintenance – has led to their use on space probes, where the steady decay of radioactive material warms the thermoelectric material to create electricity.

The company puts the cost of tetrahedrite at about $4 per kilo compared to between $24 and $146 for other thermoelectric materials. Scullin says a thermoelectric system in cars today based on it could lead to net fuel and greenhouse emissions savings of up to 5%. That is double the saving other car prototypes have achieved to date, he says.However, Alphabet Energy’s material – based on the mineral tetrahedrite – amply satisfies requirements. First developed by researchers at Michigan State University but exclusively licensed to the company, the raw ore is abundant, environmentally friendly and easy to manufacture into the material on a large scale, says Scullin. It is also more efficient than existing thermoelectric materials.

Jeff Snyder, a thermoelectrics expert at the California Institute of Technology, says little information is available publicly about the company’s tetrahedrite technology so it is hard to know if it is onto a breakthrough. But he added it was good to see a product like the E1 thermoelectric generator finally coming to market, though the cheap cost of fuel might make it hard to win traction. “Thermoelectric materials are great in principle,” he says. “The real reason it doesn’t get done is simply economics.”

He added that the technology was difficult to apply to car exhausts because the engine temperatures change as we stop and start. Thermoelectric materials work best when the heat is constant. Payback times would also be longer than for a continually operating machine like a power plant because we don’t drive all the time.

Eventually Scullin sees applications of Alphabet Energy’s technology to consumer devices. Maybe the dryer could power the alarm clock, he suggests. “The coolest thing about what we are doing is making people recognise that this thing that’s all around them, waste heat, is actually valuable.”

Wind power is produced by using wind generators to harness the kinetic energy of wind. It is gaining worldwide popularity as a large scale energy source, although it still only provides less than one percent of global energy consumption. 

Splitting water into hydrogen provides a means of harvesting the hydrogen for fuel. This image depicts the water-splitting process in a light-sensitive electrode material (BiVO4), which UChicago and University of Wisconsin researchers investigated in an experimental and computational study.An inexpensive method for generating clean fuel is the modern-day equivalent of the philosopher's stone. One compelling idea is to use solar energy to split water into its constituent hydrogen and oxygen and then harvest the hydrogen for use as fuel. But splitting water efficiently turns out to be not so easy.

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