80 Watt 12V Monocrystalline PV Solar Panel – £69.98 inc Delivery!

Posted on April 12, 2013 by neil

Special offer of the week has to be these 80 Watt power monocrystalline PV Solar Panels offered as a pre-order item (to be despatched after 17th April 2013).

The panel, pictured above, has an anodised aluminium frame, 3.2mm tempered glass, and is 824 x 669 x 35mm and just 8kg. Best of all is the price – £64.99 plus £4.99. It comes fitted with standard MC4 terminated cables. It is fully weatherproof for outdoor use.

Click here for more information or to snap up one or more of these panels now: 80 Watt 12V PV Solar Panel.

New Solar Cell Efficiency Record – Spectrolab

Posted on April 10, 2013 by neil

Back in 2007 we announced that Spectrolab (a subsidiary of plane-maker Boeing) has set a new world record for solar cell efficiency at 40% with a multi junction solar cell with concentrated sunlight (with lenses or mirrors). That record was subsequently broken, but is still around 41%.

Now Spectrolab have announced that they have broken the world record for solar cell efficiency without solar concentration achieving 37.8% efficiency, and they believe that the technology they used to achieve this is capable of getting to efficiencies of eventually getting up to 45%.

Spectrolab specialise in making high efficiency multi-junction PV solar panels for use in space to provide power to satellites, but their technological advances will eventually work their way down to the consumer market. Increasing the efficiency of solar panels is important, because high efficiency means physically smaller panels which need less materials, cost less to transport, and can be used in more situations.

L298N Dual H Bridge Motor Drive Controller

Posted on April 8, 2013 by neil

An H Bridge is a electronic circuit which has an output voltage which can be in either direction. This is particularly useful when used with motors as reversing the polarity of the power supply to a motor causes it to rotate in the opposite direction.

In our article Automatic Hen House Door Controller we showed how a pair of relays could be used to achieve this polarity reversal for motors, as making an H bridge can be a bit complicated and mistakes tend to lead to destructive short circuits. Fortunately now there are many ready made H bridge boards available relatively cheaply which make everything a lot simpler for the DIYer.

Pictured above is one such H Bridge circuit. Like most it is actually a dual / double H Bridge and so it can be used to control the direction of motion (and on/off status) of one or two motors.

The row of three screw in-terminals pictured at the bottom of the image are for the +12V and GND input connections, and a +5V output connection respectively. The +5V comes from an onboard 5V regulator which can be used to directly power a microcontroller such as an Arduino or Picaxe which would usually be used to control the motor(s).

The pair of terminals on the left of the image connect to the two power inputs of the first DC motor, and the second pair of terminal on the right to the second motor (if used).

There are 4 yellow inputs on the bottom right of the board as shown in the image labelled IN1, IN2, IN3, and IN4. If a high logic signal is sent (by the microcontroller) to IN1, the first motor will turn in one direction. If a high logic signal is sent to IN2 then the first motor will turn in the other direction. IN3 and IN4 work in the same way with the second motor.

It is not actually necessary to use a microcontroller – microswitches and resistors can be used to control the motor(s) in some simple applications.

This H Bridge circuit is based around the L298N from ST Microelectronics – a dual full bridge driver which can supply up to 2 Amps of output current to each motor.

Click here to purchase one of these: Dual H Bridge Boards. Prices start from just £2.50 including delivery (air mail from China – 3 weeks) to up to £10 from UK sellers. As it typically costs around £5.00 to purchase just the L298N chip from electronics suppliers in the UK, these boards are great value and speed up project development no end.

Testing LM2596 Variable Voltage Regulator

Posted on April 8, 2013 by neil

Our LM2596 Variable Voltage Regulator (discussed previously here: regulator with display) has finally arrived after its long journey from China.

The first image above shows the input voltage as being 13.8V (which was accurate to <0.1V). The second image below shows the output voltage which we set by adjusting the small brass screw in the blue potentiometer to be 5.0V (which was also accurate to <0.1V).

lm2596 with LCD voltage display

The build quality and quality of the components used is excellent throughout, the LCD is bright, and the addition of a red LED and a green LED to indicate whether the input or output voltage is being displayed is very useful. Selecting whether to display input or output voltage is achieved using a small button on the regulator board. In addition to screw-in terminals for connection of the input and output wires, there are also holes with solder pads in both fine and medium sizes so that different sizes of wire can be more securely attached if required.

The only bad point would be that there is no option to turn off the LCD when it is not needed – i.e. it needs three options (display input voltage, display output voltage, or display nothing) instead of the two it has. The LCD draws approximately 25mA all the time, so will take 0.6Ah of charge out of a battery every 24hrs which is a lot. Another 10mA seems to be the quiescent current lost in the regulator when nothing is connected to the output but it is still regulating voltage.

We can think of many uses for these voltage regulators which are made easier thanks to the on board display – first and foremost for small battery charging from a 12V battery, and/or powering USB charged devices (using a 5.0V output). For battery charging of say four series connected NiMH rechargeables, you would just set the output voltage to say 5.8 or 5.9V and connect it to the battery pack with the correct polarity.

Apart from having slightly high self-power consumption, these regulators are excellent quality and fantastic value.

If you are interested in purchasing one of these regulators, click here: LM2596 Voltage Regulators. Prices are around £3.50 each or £17 for five including air mail delivery from China.

Rust to Help Storage of Intermittent Renewable Energy

Posted on April 7, 2013 by neil

The main disadvantage of some renewable energy sources (particularly wind and solar) compared to fossil fuels is you cannot guarantee to have the power you need when and where you need it. Wind speeds are not stable, and it can be cloudy (certainly in the UK) and its always dark at night.

In order for a very high percentage of our power needs to ever be met by renewables, it is essential that new improved ways are found to store power so that it is available even when the sun is not shining and it is not windy. Otherwise we will need more fossil fuel power stations as fall backs to ensure that electricity demand can be reliably met at peak times.

One of the cleanest ways of storing power is to use surplus renewable electricity to break water down into its constituent parts – oxygen, and highly flammable hydrogen. The hydrogen stored at times of surplus is then burned to power a turbine to generate electricity at times when renewables cannot meet demand directly. Best of all, the waste product from burning hydrogen is…pure water.

Until now the catalysts (electrolysers) used to split water into hydrogen and oxygen have been expensive, exotic, and often toxic rare earth metals such as iridium oxide and ruthenium oxide. With such high production costs it had been thought that storing energy by splitting water would never be cost effective. But, recent research from University of Calgary in Canada has found that iron oxide (rust) combined with a few other inexpensive materials can be used as a catalyst at a cost of one thousandth that of existing commercial catalysts while working at 85-90% efficiency.

This ability to split water into hydrogen commercially using renewable energy will also greatly help the future of hydrogen fuel cell powered cars. It also has a great deal of potential for off grid renewable systems currently using batteries for storage, but which will soon hopefully generate their own hydrogen for a small hydrogen powered generator replacing their existing polluting and expensive to run diesel generator.

The Cost of the Move to Biomass

Posted on April 6, 2013 by neil

There is an article in this weeks Economist which looks at the potential downside of the EU’s move toward Biomass as a means to reach its target of generating 20% of its power by renewable energy.

EU planners want 1210 Terawatt hours (TWh) of energy to come from biomass by 2020 (compared to 500 TWh from wind power). The majority of that biomass will be used to heat things – primarily in domestic wood burning stoves and boilers in Eastern Europe, but there will still be more electricity generated by burning the remaining 20% of the biomass than from all solar and offshore wind turbine generation.

While some of the biomass will come from crop residues and other waste products, the majority will be from wood – trees from sustainable forestry.

While this is seen as being carbon neutral – plant a tree, it absorbs carbon, burn that tree, it releases the carbon, plant a new tree, and so on, in reality this is not the whole story. Biomass power stations need fuel, and large power stations need a lot of fuel – far more than can be sourced locally. Therefore huge volumes of biomass material need to be processed (using electricity – probably not renewably generated) and moved hundreds or even thousands of miles from forest to power station (most likely using diesel).

3.3 square kilometres of forest per 1MW of output from a biomass power station, so huge swathes of biodiverse natural ecosystems are likely to be displaced by unnatural plantations with the loss of wildlife habitats and other environmental issues.

The Economist’s argument is that with all these problems, public money should not be spent on biomass subsidies which distort the market, and instead ‘the market’ should be left to choose the cheapest and cleanest renewable technology (and to invest in future renewable technologies) by setting a carbon tax which makes fossil fuels more expensive to use.

Autonomous Robot Solar Panel Cleaner

Posted on April 2, 2013 by neil

With huge growth in solar electricity generation in North Africa and the Middle East recently a problem keep recurring – how to keep solar PV panels clean in arid regions with virtually no rainfall and lots of dust. A sandstorm can cover panels with a layer of dust in minutes which will reduce their efficiency by 80-90%.

One way around this problem is to use the some of the solar electricity generated to run a desalination plant to get fresh water to clean the panels, but this is very inefficient and expensive, and requires the solar array to be installed near the sea.

Miraikikai Inc have an existing commercial product called WallWalker (pictured above) which is an robot wall and window cleaner. It is primarily designed to be used to clean inaccessible windows adhering to them using suction and zig zagging its way up and across them while cleaning.

Pictured above is their new prototype automomous solar panel cleaning robot developed in conjunction with researchers at Kagawa University. It weighs in at around 11 kg and has a battery life of two hours. Its rotating brush cleans the solar panels as it passes over them without using any water.

It is hoped that a commercial version of this prototype will be ready for sale by this time next year (spring 2014) ready to meet demand.

Swansea Bay Tidal Lagoon – Tidal Power

Posted on April 2, 2013 by neil

The UK is blessed with the second highest tidal range in the world. Having such a big vertical difference between high tide and low tide makes tidal power an attractive and realistic renewable option.

The Bristol Channel between England and Wales acts as a funnel resulting in the typical 0.6 metre tidal range of the ocean increasing to 9 metres. For this reason for decades their have been plans to build the Severn Barrage – a 10 mile dam between England and Wales which could provide an average of 2GW of power.

While the Severn Barrage has never been built because of the environmental impact and financial costs, a public consultation is about to start for the proposed Swansea Bay Lagoon – a 9.5km long wall 11 metres above the low tide enclosing 9.4km² of water around Swansea Bay, Wales.

Proposed Swansea Bay Lagoon - tidal power

200-250MW of low head bulb turbines of the type used successfully in La Rance Tidal Power Plant in France would generate electricity as the sea enters the lagoon on the rising tide, and leaves the lagoon on the falling tide. This would generate 400 GWh of electricity per year which is equivalent to the domestic consumption of the whole of Swansea (107,000 homes), and would cut carbon emissions by 200,000 tonnes per year.

The design life for the lagoon is 120 years meaning 120 years of reliable and wholly predictable tidal electricity generation. It would be the first man made tidal lagoon in the world.

The predicted cost of the Swansea Tidal Lagoon and associated development and infrastructure is £650 million. It would take 2 years to build the wall and if given approval, this tidal power station could go online as early as 2017.

For more information click here to visit the official Swansea Bay Tidal Lagoon website.

9V from 12V Regulator Module – Alternative to L7809

Posted on April 1, 2013 by neil

About six months ago a Chinese company on eBay had a special offer selling the item pictured below for US$2 each. We bought five and put them somewhere safe and then forgot what they were for.

A quick test today showed them to be efficient 9V from 12V regulators working much the same as the common L7809 regulator.

With a bit of searching around we finally found the details for this product. It is an high current voltage regulator which takes an input voltage of from 12-23 VDC and outputs 9 VDC. No heat sinking is required up to a constant 2.5 Amps of output current, and they are rated to supply brief peaks of up to 4 Amps.

The pin connections (the three legs) have 2.54 mm (0.1 inch) pitch exactly the same as for the L7809 regulator, and the device is also of similar overall dimensions. Therefore, this little PCB can be used to substitute an L7809 (pictured below) where more current than the 1-1.5 Amps (with heat sink) maximum of the L7809 is required.

It could for example also be used instead of the LM317T we use in our standard 9V from 12V regulator (though we have designed that with R1 = 330, R2 = 2K8 so that we get an output of around 8.8V compared to the 9.3V this regulator module outputs – a lower voltage to reduce power consumption for renewable energy powered applications). With thicker cables for the connections this would give a 2.5 Amp constant current 9V from 12V regulator with no need for heat sinking.

This module has a small integrated circuit labelled MP2307DN which a quick search on Google shows up as a 3A constant load current DC-DC step-down power supply module and a monolithic synchronous buck regulator, which has been used in this case to provide a 9V output.

At the time of writing we can only find this device here: L7809 Alternative Module priced at US$4.99 plus US$1.99 for air mail delivery. (The same vendor also has similar L7812 and L7833 alternative modules for 12V and 3.3V outputs respectively.)

Project PCB Boards for 18-pin PIC Microcontrollers

Posted on April 1, 2013 by neil

We use microcontrollers every day for many of our projects, mostly 8-pin but quite often 18-pin for the more complex products we are requested to design and build. We have found the following products to be particularly helpful for prototyping and for one-off projects – 18-pin project PCBs from UK company RK Education.

Pictured above is a RKP18HP board designed for use with 18-pin microcontroller such as PICAXE. This board gives 5 inputs, and 8 TIP121 power transistor outputs for high power applications. It is supplied with a software download socket to get your code onto your microcontroller.

Below is the RKP18Relay8 board which is again designed for 18-pin microcontrollers and takes up to 5 inputs and controls 8 SPDT relays each with LED indicators to show then they are energised. Again the software download socket is provided.

These items are available as just boards (PCB) or as full kits and are very competitively priced – transistor board £1.19, kit £3.49; relay board £2.00, kit £10.99. The kit prices include all the components shown – e.g. all the relays, screw in terminals, LEDs, resistors, etc, so all you need to add is your choice of 18-pin microcontroller and you need some solder and a soldering iron.

The power transistor board takes about 10-15 minutes to solder together, and the relay board around 15-20 minutes. Full instructions are provided and the PCBs are well labelled so it is difficult to make any mistakes.

Many other boards are also available for low power applications, smaller and larger microcontrollers, and much more. For a one off 28-pin or 40-pin microcontroller project (e.g. PICAXE 40X2 as pictured above) the corresponding boards with large prototyping areas are particularly useful.

Take a look at the RK Education website here.

REUK.co.uk

The Renewable Energy Website

Monthly Archives: April 2013