Wednesday, 8 February 2012

Diesel Generator or Solar Panel.

I like the idea of a back-up power supply using a Diesel generator. However, I have to ask myself would solar panels or a wind generator provide a good source of electrical power as an alternative. I have chosen to use a diesel generator over petrol as my boat  insurance precludes the carriage of petrol.

A diesel generating set could provide a guaranteed source of power at any time day or night. There are diesel devices available providing power from 2kw up to 6kw which would fall within our requirements and budget. In respect to convenience a generating set has a lot going for it. However, it is not acceptable to be running a generator late into the evening. There are problems of the noise disturbing others moored nearby. So the convenience over solar and wind is not so clear cut as one might at first think. The cost of a generating set is controlled by the output power  available and the hours per litre running costs. The operating life is difficult to predict but there are going to be wear and tear replacements as well as the usual servicing costs. Electrical safety levels should be pretty high though some engine parts maybe hot. Storage is going to be a requirement as even the low power generators can be heavy and cumbersome. The generator would not normally be used when the boat is underway and providing charging power from the on board alternators.

Estimated purchase cost £600.  Estimated Running cost for fuel £1 per hour.  Estimated Maintenance costs £1 a week. A total of £850 pounds for the first year and £200 per year until a replacement is required. (10 years)

Solar Panels are subject to the vagaries of the English weather. They may require some occasional adjustment to align the panel into the sun. The adjustments are needed to get best efficiency from the panels. Costs are still falling and have dropped by about 25% in the last two years. I expect this trend to continue for the next few years. Typical system would be based around a 200 watt budget delivering around 17 amps of charge to the leisure battery pack at peak performance. The reality is that the daily average is going to be closer to 20% and in the region of 3/4 ah. The operating life is going to be in the region of 25 years. As the panel is a renewable energy source, fuel comes free. Maintenance will be minimal and restricted to the occasional wash and brush up of the panels. The panels are quite safe to operate however, the usual care being needed as there can be large currents circulating. Fitting is easy and not expensive even if done by a fitter. Storage will depend on local conditions and how secure the panels are mounted. The device will not have to be removed and stored when travelling on inland waterways. The breakdown on panels is about 90p per watt and a good quality charge controller in the region of £200. The power will still be generated by the panels when the vessel is underway but at a reduced performance. The system is easy to expand by adding further panels at a later date (subject to the maximum power capacity of the charge controller)

Estimated purchase cost £600. Estimated Running cost for fuel £0 per hour. Estimated Maintenance costs £0 a week. Say 700 pounds including fitting for the first year and £0 per year until a replacement system is required. (25 years)

Wind generator. I have little experience of this type of system, but like solar panels it is going to be subject to the vagaries of the English weather. As the device is a renewable energy source fuel comes free. Cost is going to depend on the amount of power that is required to be generated. The devices can be used at night but from my experience there can be low levels of wind noise associated with the device. The device will have to be taken down and stored when travelling on inland waterways. There are moving parts and so care must be taken when coming close to the device.

Estimated purchase cost £600. Estimated Running cost for fuel £0 per hour. Estimated Maintenance costs 50p a week. Say 700 pounds including fitting for the first year and £25 per year until a replacement system is required. (10 years)

From the above I have discounted a wind generation system as not being practical or convenient for us. So now other external requirements are going to come into play.

Charging a battery powered cycle and running a washing machine when off mains. Are part of our requirements. The cycle we don't think will be a major problem either way. The washing machine is going to be the single deciding factor. Rated at 1300 watts, this is easily inside the capacity of our inverter. Our battery bank is rated at 500 Ah. At an estimated current draw of 120ah from the battery pack for a complete washing cycle. We will only do our washing whilst the boat is under power. The alternator will therefore provide some of the power to the load. A diesel generator would be able to provide the power without using the inverter pack when moored up. However, it would not be practical to run it when on the move. Therefore the solar panels are proving to be a very cost effective item for providing some free power over a long term period. So we have decided to go that route with the caveat that if the solar/alternator combination is not able to maintain a weekly wash then we will also purchase a diesel generator as a back-up.

Making solar panels that are as efficient as possible at turning sunlight into electricity is not easy. It's a way to bring costs down (you need fewer solar cells for a given output) and keep the footprint of solar installations to a minimum. Typical efficiency for a modern solar set-up is around 15% however technology changes are playing a big part in improving the solar output.

The latest efficiency record was achieved by a company called Semprius. Their technology uses lenses to concentrate the sun's rays onto high-performance solar panels. The actual solar cells might only be a few square millimetres, but the lenses provide them with light that is as intense as 1,100 suns, so what they lack in surface they make up in intensity and efficiency. So the new solar record is 33.9%, which is 2% higher than the previous record.

Scott Burroughs, vice president of Semprius said “This is a significant milestone for Semprius and the entire PV industry. For the first time, we have been able to convert more than one-third of the sun’s energy into usable electricity. This demonstrates how concentrated PV can leverage rapidly increasing efficiencies to continue driving down the cost of solar generated electricity.”

How soon will this technology change take to filter down into consumer installable equipment is open to guesswork. But amateur installations using mirrors to increase the sunlight falling onto standard panels have given system efficiencies over 20%.


1 comment:

  1. Interesting points. I've also been questioning these to myself if the diesel generators are better than the solar panel. And yes its not good to use generators at night because it would disturb your neighbors but I also heard that there are some generators that doesn't make any noise or too much noise.. So you just have to weight it too :)


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