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Alternative electricity soures?

We have been set a challenge by our HQ to come up with ideas to improve the current electricity supply problems.

The Power from the grid is intermittent and there is a sever shortfall in its capacity. We have a limited amount of money to come up with ideas to give more electrical power to the local community.

Ideas such as micro power generation would be ideal, but they have to be cost effective. Ideally be constructed locally.

I have investigated ideas such as micro hydro at the local canal but these systems seem to only give a small electrical output. How about Bio-methanol generators systems. Do they require much infrastructure?

I hope I have given you an idea of the type of solutions we are looking for.

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bio generators need heat and time: heat to promote the chemical reactions, time to allow the process to run. A lot of raw material is needed for a small output.

the canal may provide small electrical output, so is there any way to leverage it? is there a lock which has a natural fall to accelerate the water?

small wind generators are available, but maximum wind will not coincide with maximum demand (in fact it may come at the worst times)

solar cells might work, especially with a UPS: the cells can charge the battery while there's grid power, and the batteries plus the cells can run loads when the grid power is off.

for something quick (and dirty!), a diesel generator is still the best hope, but it will need maintenance. Anything else will require infrastructure.

What efforts have been made to characterise the demand? For example, is there any prospect of rationing usage when the backup power is being supplied? Are there any obvious losses in the system, for example very small wires feeding large loads? Can you identify critical and non-critical loads?

Regards

Mike Ennis

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Reply:

Please see come comments in answer to your questions.

There is a canal nearby with a lock. But when I have investigated micro hydro units they can only produce 100 - 200 Kva for those types of systems. Can you procure larger hydro units that are designed for canals and locks?

As for you question in regards to demand. we are trying to power large residential areas which already employ all efforts to reduce electrical consumption during the evening. Could you please explain more about solar cells? Are these solar powered batteries which charge the battery during the day to be used at night?

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I experienced similar grid problems in various parts of Africa. There are several approaches, but none are particularly cheap or local:

1) Provide localised back-up using engine generators, probably diesel. may be possible to convert these to run on old vegetable oil - need to strain it and keep it warm, and increase injector pressure a bit. More basic engines, and especially ones with chunky injectors e.g. Mercedes; work best.

2) Any microgeneration scheme needs to guard against back feeding into the grid, which is a potentially life threatening risk to anyone working on the distribution system. Clever inverters e.g. Trace SW range, can take account of this and disconnect the grid and only feed locally when the grid fails. It can also be done using a contactor between grid and local distribution that is held in by the grid. Grid fails, connection is broken. However, this needs a manual reset because if it automatically reconnects when the grid returns, you inverter or generator is unlikely to be synchronised and the result will be fried electronics, most likely at your end.

3) Simplest system is an enlarged uninterruptible power supply (UPS). Use an inverter-charger to keep a bank of batteries full. Grid fails > charger becomes inverter and generates mains supply from the energy stored in the batteries. Safety measures in (2) apply to prevent back-feed and synching issues.

4) Photovoltaics, with batteries and inverters can provide long term off-grid power but will be expensive if you want to run heavy loads like conventional fridges and air-con. Forget any form of electric heat - cooking, kettles, etc. I work for a company that has been supplying PV systems for medical applications, particularly in Africa, for 20 years: www.dulas.org.uk

5) If it's very windy, small wind turbines could be an option and can be made locally. They don't produce much though, and it really does need to be windy a lot of the time. Larger turbines can be linked with diesel generators to form wind-diesel hybrids that can run localised grids of tens or hundreds of kilowatts. Specialised kit and needs the wind, but quite a robust system.

6) Hydro is best where the water falls some distance - at least 10 metres is good. Low head is also possible but needs high flows so turbines and civils are bigger and more expensive. Power = flow x head (height of water fall)

Hope that provides a few ideas. Happy to add more detail if they want to take it further.

Duncan Kerridge

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This is quite an interesting problem and given lack of budget, options is limited.

The end game should be better provisioning from the grid, that will take big funding and a lot of resources.

To reach the best solution, it is important to assess needs and the status of the power supply as it stands now. The assessment should look at what the essential needs are and then try to fulfil the top priorities.

Hydro systems have limited use. When water dries up, then there is no means to generate power. Bio fuel or diesel will depend on secure supplies on an ongoing basis. I personally do not feel that the implementation of many generators in each house will be the best solution. Centrally generated power in lager power stations is usually the most cost effective.

The best way to approach this is to work out what the consumption needs are for each building. Lighting and perhaps communications should have some sort of priority. Given that power does exist occasionally, the best solution is to have a charger/inverter arrangement to store power. This may be supplemented by solar and perhaps wind systems.

I can provide more specific ideas if I am given some more detailed information regarding the actual needs.

Regards

Mark Hawkins

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ultimately the output of any hydro scheme is limited by the head and the flow rate, and your project worker may have established 200 kVA as the limit.

This link offers calculators for small hydro, and info on a variety of backup power systems.

http://www.nooutage.com/index.html

if the problem is one of both insufficiency and intermittency, then it seems any backup option has to have the ability to provide storage from renewables when grid power is available, and then combination of storage and renewable when the grid power goes away.

Because these "backup" systems are limited in capacity, I don't see one single solution as working; a combination will be necessary.

Finally, what does the project worker regard as "large residential"? If 200 kVA is way too small, and the average residential load is maybe 2 kVA, then we're talking about residential areas encompassing

  • 500+ dwellings? -1000+ dwellings?

Are there also business and small industrial/commercial users on the system?

Mike Ennis

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Asked:
2013-12-09 08:07:25 -0500
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Last updated:
Dec 09 '13