Archive for the ‘Photovoltaics’ Category

How to Understand Microgeneration – Solar PV

Friday, April 9th, 2010

Presentation made before smart metering and feed-in tariffs (FITs) now available.

 

 

Photovoltaic Modules and Inverters – Considerations for Selecting

Saturday, April 3rd, 2010

With so many different types of products on the market today for the solar electric (PV) industry, selecting the right module or inverter can be the difference between a successful system and a failed one. The PV market has hundreds of companies to choose from when selecting product. Being that longevity is one goal in providing an extended return of investment (ROI) for projects, it is important to select the products from companies that you can trust will be around into the distant future.

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Research can be a daunting task in regards to finding the balance of quality, longevity, and price — your distributor can be a great source of information when considering products for a PV systems. Your representative should be able to provide you with information about product warranty, quality of the product, price (often reflected in £ per watt), and any technology implemented into the product.

As it relates to solar modules, the most expensive side to the system, a low priced module can get very tempting. While important, price should be weighed in conjunction to a manufacturer’s longevity; after all how good is a 20-25 year warranty when the company no longer exists? Additionally, there is a common miss-conception that module efficiency should be the deciding factor — efficiency generally only affects a systems size not performance. Efficiency reflects a modules ability to convert the sun’s energy into electrical power. For example a 200 Watt 16% efficient module vs. a 200 Watt 20% efficient module reflects a reduction in the system physical size by 20% but this will also most likely increase the cost of the module and therefore the length of ROI on the same 200 Watts of power. Until just recently, module technology was mostly based only on efficiency and material type, but now some electronic technology is implemented into the modules themselves increasing the modules energy yields, and power output.

This seems all very familiar to me, relating the subject to the debate I’ve had before on data centers design with computer equipment technology, required power per square foot / meter and increased computer rack efficiency density allowances.

Conversation would go something like this:-

  • Computers getting more efficient – so less power needed; Please reduce power allowance – Reply: OK
  • But have a higher density, so can increase the computer power in the same allocated space with more modules  – Reply: So you need more power!
  • But we need less overall space per module, so more efficient: As a result the computer power is greater – Reply: You need more power per sq area – in less space!
  • Oh! – but the computer module is more efficient – so less power needed – Reply: Yes individually – but you put more in!

Inverters are also a key function to the PV system and also typically the second most costly item of the system. Inverters contain many electronic components and over the years can be stressed to their limits, so selecting a manufacturer that has proven technology and a solid warranty can help save the installer a problem down the road. In the past the PV market has seen typically a 10 year inverter warranty and a fail period on the inverters in the first 15 years, however with today’s leading manufacturers these numbers are progressively getting better with 15+ year warranties and a fail period after the first 20+ years.

Solar generation – Photovoltaics an introduction

Tuesday, May 19th, 2009

Solar generation

Photovoltaics and other methods of converting sunlight to electricity

There are several accepted ways of converting solar radiation to electrical power.

Photovoltaics

The sun’s energy can be converted directly into electricity using photovoltaic cells. PV cells can be used for applications as small as watches and calculators, to large grid-connected arrays of panels. The great attraction of PV technology is that it delivers electricity at the point of use, for example panels can be integrated into buildings to supply the buildings themselves.

In areas where grid connection or other forms of generation are too expensive or not feasible, PV can be very cost-effective. This may be in remote locations, but could also be in a city centre where grid connection may be impractical. For example it can be cheaper to power parking meters with solar energy than with power from the grid.

PV materials are usually solid-state semiconductors. various forms are used:

  • Mono-crystalline silicon
  • Poly-crystalline silicon
  • Amorphous silicon thin film
  • Thin film cells of other materials such as copper indium diselenide (CIS) and cadmium telluride
  • Organic solar cells

Other technologies are also under development

Solar thermal power generation

Technologies also exist to collect the sun’s heat and use it generate steam, which then produces electricity using a conventional turbine.

One notable example of this approach is the solar ‘power tower’ approach where fields of mirros are used to focus the sun’s rays onto a boiler at the top of a tower.