sunny solutions

Multiple regulators on one battery bank

2008-06-18T12:28:00.001+01:00

Hello. I have 2 sets of solar panels (200W each) with their own regulator, and a wind generator with its own regulator. However they are not all charging efficiently. Even though the battery bank is fla,t when it is sunny and windy the wind regulator slows the wind gen down and one solar reg beats the other down. So I am getting maximum recharging from only one source not all 3. I think the regulators are sensing the charging voltage of the dominant regulator and thinking the battery is fully charged. Any suggestions? I have been looking for a regulator to manage 3 inputs (and 2 outputs would be good) but can't see any. Could I wire all 3 regulators to a 4th regulator for the bank? Thanks. Stephen.

Hi Stephen. You are right that whenever you are charging a battery, the voltage will increase, and therefore any other charging sources attached to the battery will see a higher voltage and think the batteries are slightly more highly charged than they actually are. That's pretty much unavoidable.

The effect should not be very large, however, and it's not necessarily a bad thing, as it prevents overcharging. PV arrays trickle charge batteries, and with a healthy battery bank and decent sized cables between the battery and regulators, you shouldn't see a massive voltage increase. If you are - if they are cutting out even when you think the batteries are flat - it's suggesting the voltage is rising above 14.4V (the usual cut off), even with a relatively low charging current. That suggests to me that the batteries are on the way out.

Regulators are designed to be used in parallel in the way you have them wired, so I very much doubt you will find any difference if you do change the regulators. Trying new batteries is in my opinion far more likely to give you good results.

Hope that helps.

Lizard heating by solar power - is it practical?

2008-06-05T08:38:00.001+01:00

Hi - I was wondering if you could help me, I'm looking to buy solar panels for my garden shed but don't know what one would be suitable. In the shed I have a glass tank with a lizard in it and I would need the panel to power an 80w fluorescent tube that is on 12 hours a day and a 190w ceremic heater bulb which is on 24 hours a day. Can you help? Cheers Andrew

Hi Andrew,

You can use the solar panel calculator to work out how big a solar panel array you would need. But I can tell you now that running a heater all the time would require a huge array unfortunately - 190W is a very big load to be powering for 24 hours a day. In fact I usually reckon that in the depths of winter you need a solar array with a rating of 20 times the average power draw of the equipment you want to power, as on cloudy days you don't get a big return from the panels. So, for a 190W continuous load, you would need about 3800W of solar panels - which would cost over £10000 and wouldn't fit on your shed roof anyway. Sorry!

If the ceramic heater is on a thermostat and is only actually on 10% of the time, that would make a huge difference - it would drop the array size to only 380W, which might just be practical.

Expensive lizard. Even on mains electricity you are burning about 5.5 kWh per day with that light on 12 hours a day and heater on continuously; at 13p per kWh that works out at over £250 per year.

Solar panels on garden shed

2008-05-15T16:12:00.001+01:00

I know nothing about how to set up a solar panel system. I am wanting to get power to a garden workshop to run a light, and power a plug socket for using small electrical equipment eg. soldering iron, drill. What products would you suggest would be suitable and how would I set them up?

Hi Jennifer,

A solar panel system is extremely simple - a solar panel charges a 12 volt battery (usually through a regulator, a little circuit that prevents the panel overcharging the battery), and then you can power your appliances off the battery. Many appliances are designed to run directly off 12 volts - anything that plugs in a car cigarette lighter socket for example - but you can also use an inverter to convert the 12V from the battery into 240V to power standard household appliances.

In your case you would need:
1) a solar panel kit (which includes the regulator and wiring) such as our 40W kyocera solar panel kit.
2) standard 'leisure' battery, available from any motoring store
3) a 12V light to run directly from the battery (eg the Labcraft Trilite),
4) an inverter such as the 500W model, in order to run 240V appliances such as power tools. For bigger tools you might need a bigger inverter - the 1000W model would be more than adequate for most household power tools.

The 40W solar panel kit should be adequate for occasional domestic use in a shed. If you were using the system for more than an hour or so a day on average you might need a bigger panel.

Do hope that helps. I know quite a number of people who have done similar things on their garden shed - it is pretty easy to set such a system up.

Is an 80W panel sufficient for a motorhome?

2008-05-12T08:16:00.001+01:00

Have just bought a motorhome and want solar panels suitable for long term living in van. Would your 80w panel be sufficient, and what other items would I need ready for fitting this panel on my van?
Thanks - Andrea

Hi Andrea,

Whether 80W is sufficient depends entirely on what appliances you want to power! In the summer, for a few lights / water pump / radio etc it would be more than adequate; in the winter it might not be enough, especially if you also want to run things like a TV, laptop, or fridge.

Try our solar calculator to get an idea of what appliances you might be able to power.

If you buy the 85W solar panel kit it includes the regulator and all the wiring you need for fitting the panel. The only other thing you will need is some means of mounting it on the roof - it shouldn't be too hard to make up some suitable mounting brackets.

Solar for heat gun and lighting

2008-05-08T09:28:00.001+01:00

Hi - I am going to start a business car window tinting in a standard basic garage; however I have no means of electric so I wonder if you have a solution. I need enough energy to power a normal light supply and also to be able to power a heat gun for 2-3 hours (not constant) a day. I do not have lots of money so would be looking for the cheapest solution. Thank you - Kieran

Hi Kieran,

It's possible - but it might not be all that cheap!

You can use our Solar panel calculator to work out how big a system you need. For example, a 40W light for 4 hours and a 1000W heat gun for 30mins per day would need about 516 watt-hours of electricity each day. 200 watts of solar panels would give you that much for most of the year, but probably still not enough in winter.

Some idea of the costs:

200W solar panels - about £800
regulator - £95
batteries - about £150
inverter - £148.

So it does add up!

regards, Andy

Running 240V appliances by solar power

2008-05-08T09:07:00.001+01:00

I would like to build a device where a solar panel is connected to a UK standard plug socket, to power UK standard (240 volts I think) electrical appliances. As far as I am aware I need a solar panel, a diode, a regulator, a battery, an inverter, and a plug socket. The unit would be stand-alone, not connected to the national grid, but able to power standard 240v electrical appliances, e.g. electric kettles.

My questions are these. Is this project possible (I assume it is, beacause it can be done on a larger scale by linking solar panels into the house mains electricity)? How do I calculate the energy input output requirments of the components (can I use any components of different energy flow allowances with each other)? Do the components have to be conected in a special way?

Thank you, Chris

Hi Chris,

Yes, the project you describe is certainly feasible, and in fact it's quite common to use solar power in this way to power 240V appliances where you don't have a national grid connection.

You can use our solar panel calculator to work out how much power your appliances will take, and how big a solar panel array would be needed to power them. The inverter size you need depends on the maximum power you need to draw from the system - so a laptop charger would be fine with a inverter of a couple of hundred watts; a kettle however would need a 2kW inverter at least.

You don't need a diode in the system if you have a regulator - the regulator stops the panel discharging at night.

regards,
Andy
Midsummer Energy

Solar powered cool box

2008-05-06T10:01:00.001+01:00

Hello - I am looking for a solar panel which I can use with a cool box in our motor home. At present the box connects into the cigarette lighter. Is there a panel that has the facilty for plugging in such an item? Thank you - Tony

Hi Tony,

You could fit a cigarette lighter socket to any solar panel very easily, which would allow you to power your cool box directly. Something like the Spectra 20W panel might just be big enough to power a small cool box.

However, you should note that the voltage on a solar panel varies strongly depending on what appliances are attached to it and how much sun there is. Some appliances can accept a wide range of input voltages and would be fine with the variable voltage; others might not like a voltage of perhaps 18-20V applied to them! When you are running off a battery the voltage is very stable, normally between 12 and 14 volts.

Most cool boxes run on peltier cooling modules, which I am fairly certain would work fine when attached directly to a solar panel. However, I can't promise that it would work.

regards,
Andy
Midsummer Energy

Battery types and powering appliances directly

2008-05-06T09:49:00.001+01:00

Hi, Could you please tell me in your opinion what is the best battery to use with solar power. Life span and cost are of paramount importance. Also, can you use solar power on very sunny days without charging batteries? Direct to a cooker? I am just learning/starting out to put solar on a caravan/motorhome. Thanks - George.

Hi George,

Standard leisure batteries available from any motoring store are absolutely fine for most purposes on caravans and motorhomes. As long as they are kept well charged they will have a lifespan of at least 5 years - it is batteries that are poorly charged that soon loose their capacity and need replacing.

'Sealed lead acid' or 'AGM' batteries will tolerate being discharged deeper than standard leisure batteries (and also never require topping up with water). But the extra expense is not worth it in most applications.

Cookers consume very large amounts of power - normally several thousand watts. You would need an enormous array of solar panels to power a cooker. It wouldn't really be very practical! In general you are much better storing the power from the panels in batteries rather than trying to use it directly.

Power from horizontal solar panels

2008-04-25T12:14:00.001+01:00

Hi. We wish to use solar panels on the roof of a narrow boat, but we do not want to be turning and tilting these panels. So they will be horizontal. Is it better to use the polycrystalline or amorphous panels in this situation? Regards, Jim.

Hi Jim,

It doesn't make a great deal of difference to be honest - with almost any panel you will reduce the output by about 1/3 in UK latitudes by keeping it horizontal. But personally it's exactly what I do on my own narrowboat - I reckon the saving in hassle in not having to reposition the panels every time I move is worth the small reduction in power!

The Unisolar panels (both the framed and adhesive-backed versions) do perform a little better in indirect light than crystalline panels such as the BP Solar and Kyocera panels, so might give you a tiny bit more power in a horizontal position. I would particularly recommend the adhesive-backed panels as a great solution for narrowboats. They are more expensive, but they are extremely easy to fit, virtually indestructible, and look fantastic.

hope that helps

Solar for off-grid house in Spain

2008-04-23T09:07:00.001+01:00

I would like the price for a full solar energy system to be installed in Spain to run 2 small 3 bedroom houses which have just been built side by side.

The system needs to be off grid, and able to run all potential electric mod cons (though not air conditioning). Thanks, Mike.

Hi Mike,

A typical household in the UK uses around 12.5kWh per day. On a
typical UK summer's day you would need an array of around 2500W of
solar panels to generate sufficient electricity over the course of a
day to replace that power.

On the one hand you have better sun resources in Spain, and with
energy efficient appliances you can reduce the 12.5kWh needed per day
considerably; but on the other hand there will be times - overcast
days in winter - that the panels produce less than 12.5kWh per day. On
balance, a 2500W array will give you a pretty good amount of power to
play with - but you do have to remember that fundamentally a battery
bank is a limited resource, and if people leave all their appliances
on over a couple of dull winter days it will run out!

Your battery bank needs to be capable of storing considerably more
than one day's power, as it's bad for the batteries to be heavily
depleted, and also you have to have a good reserve for those overcast
days when the panels are not doing very much. As a minimum, I would
say a battery bank of 40kWh for a 2500W array.

So, the system components for each house would comprise:
- 2500W of solar panels. Approx cost £9000.
- 32 x 110Ah 12V batteries (capacity= 32 x 110 x 12 = 42240Wh).
Approx cost £2500
- Solar Regulator. Approx cost £200.
- Inverter to produce 240V AC from DC battery bank. Approx cost £1500.
- Wiring, mounting system etc. Estimated cost £1500.

So total system cost is around £14700 per household, plus installation costs.

You may be able to save 10% on that as the figures I have quoted
include VAT of 17.5% - there is a lower rate of 5% on energy efficient
installations on houses in the UK, which you may qualify for.

The cost is pretty much proportional to the size of the system. It is
perfectly possible to run a household on a system half that size (and
half that cost), with careful use of electricity. Many people in
caravans and narrowboats live quite happily with solar arrays less
than a quarter that size or even smaller. On the other hand, if you
want to be able to run everything under the sun (so to speak), you'll
find that even a 2500W array per household is not enough, particularly
in the winter.

Hope that helps - Andy

Powering 5V remote instrumentation

2008-03-18T12:32:00.002Z

I'm looking for a solar-powered power supply for some instrumentation. Needs to provide 2.5W at 5v continuously (ie 24/7/365 and including midwinter) initially at sites in Southern England. Something like 99.0-99.5% (ie but <100% is acceptable) availability would be the target. We're looking for the most cost-effective solution to this requirement. Thanks, John.

In order to size your system to provide enough power in the middle of winter even on overcast days, it's best to work on a rule of thumb of a panel array of about 20x the continuous power draw of the instruments. So, for 2.5W continuous load, I would recommend a solar panel of about 50W. Obviously in the summer that will be giving you a power output way in excess of what you need - but you do unfortunately need that extra power to make the most of short winter days when the panel output will be much lower than rated.

Although you require only 5V, solar panels are almost invariably designed to charge 12V lead acid batteries, and your best bet is definately to use a conventional solar panel - regulator - lead acid battery set-up, and use a DC-DC converter to convert the 12V back down to 5V for your instrument.

The most cost effective solution would be to use our 50W solar panel kit in conjunction with a lead acid battery and DC-DC converter. You would be using about 5Ah per day, but in practice you want a battery with considerably bigger capacity as it's bad practice to discharge a battery heavily, and to ensure enough capacity for say a week of overcast conditions. I would suggest perhaps 40-50Ah as a suitable size of battery - a maintenance-free sealed lead acid type is probably best for remote instrumentation.

Life span of amorphous solar panels

2008-02-25T20:08:00.001Z

I have just taken delivery of a 62 foot narrow boat, and very interested in the Unisolar adhesive backed panels. However on the Free Solar Energy UK web site it says 'these panels offer ease of fitting but due to being based on cheaper silicon,don't offer the same efficiences and typically need replacement every 5 years- these degrade fast.' Your comments please as I am a little confused. Paul.

That's nonsense - Unisolar offer a 20 year warranty on the power output of the panels. Why would they do that if they only had a lifetime of a few years?! I've used Unisolar panels on the roof of my own narrowboat for over 5 years and haven't noticed the slightest loss of power from them. I've found them exceptionally good value.

It is true that some of the early 'thin-film' solar panels had a significantly shorter lifespan than conventional silicon panels. But it's just not true of the current Unisolar amorphous range. I'm sure you will be very happy with them if you do go for them!

Glass-glass laminate solar panels

2008-02-22T14:23:00.001Z

We have a south facing conservatory with an angled double-glazed glass roof. We are thinking of replacing the glass roof with solar panels (which produce electricity) but are struggling to find the right product. The sticky panels you sell might be an option depending on weight. But do you know of a product which would replace ordinary double glazing with similar thickness (and weight) glass panels which have integrated PV cells?

Yes, it is possible to get solar panels that are glass-glass laminates - ie the solar cells are sandwiched between two sheets of glass - rather than between a layer of glass and a sheet of metal or plastic, which is more normal in framed panels. See http://www.solarcentury.co.uk/products/low_carbon_building_products/solar_glazing for more details.

Glass-glass laminates are effectively double glazing with integrated PV cells, which sounds like exactly what you want.

The adhesive-backed panels are not particularly heavy incidentally. I shouldn't imagine the additional weight would be a problem on most roof structures if you wanted to consider them instead.

Solar panels for 120Ah per day usage

2008-02-04T17:26:00.001Z

Your suggestions please for solar panels for a narrowboat with 675Ah battery bank and 120+ Ah daily demand
Thankyou, Alan

120Ah per day is a fair demand, so I would first try to reduce demand to make things as efficient as possible! If you have a look at our solar panel calculator, in part three you can put in the power output from a solar panel array and see how much you can expect to get from it. So the 64W panel that is there for an example will give you around 26Ah in summer on average, going down to around 5Ah in winter.

The adhesive-backed solar panels we sell are definately the neatest solution. Great for narrowboats. The Unisolar or Kyocera framed panels are a little cheaper, but are not as discreet or so easily mounted. Personally I would go for four of the adhesive-backed panels, with a Prostar 30A controller - I would expect those would make you nearly free of other charging sources in the summer, although you would still need to top up by other means in the winter.

Temperature dependence of Unisolar solar panels

2008-02-04T12:04:00.001Z

I am interested in your Uni solar products, but I need a little advice.
I have a 50mm thick foam insulated (on the inside) flat, smooth, steel roof onto which I would like to mount two panels. The framed version needs to be raised and ventilated underneath for best results, but the self adhesive version must get much hotter being dark in colour and unable to dissipate heat from underneath; indeed, I understand that it must not exceed 85c.
My question is: Given that the PVL68 will get a lot hotter when compared to the framed version, how much difference in efficiency should one expect, given a hot summers day - if we get any?

Thanks for your advice. Jeff.

If you want a technical answer, the data sheet for the photovoltaic laminate series has some temperature coefficients for the different parameters, so you should be able to work out a loss of efficiency from those. See: http://www.uni-solar.com/uploadedFiles/0.1PVL-68%20AA4-3698-02.0601107.pdf, in particular the max power, which reduces by 0.21% per degree C. Note however that they say elsewhere that the temperature dependence is very non-linear, so I don't know how much reliance you can place on those figures at high temperatures. However, if a panel glued to the roof was, say, 10 degrees hotter than a ventilated framed panel, the difference in efficiency would only be 0.21 x 10, or 2.1%.

At the uni-solar web site (www.uni-solar.com) there are a few technical papers which might give you some help. Go to the home page, then select Resources > White Papers/Research reports. http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_2.pdf has a paragraph on temperature dependency for example.

If you want a practical answer, unisolar laminate panels are designed to be used in exactly your sort of situation, have a lower temperature dependence than conventional crystalline panels, and I've used unisolar panels in a very similar application myself for the last five years - on the steel roof of a narrowboat which is also insulated with foam underneath. Mine are laminate panels glued directly to the roof. I don't have any figures for the production at different temperatures, but on hot sunny days, when the roof can get too hot to touch, they are certainly kicking out a good current. I daresay there may be a little loss at high temperatures - but to be honest in any battery charging application I'd be a lot more concerned with the production at low light levels on colder days, as that is when the output is most likely to be struggling to keep up with demand.

In short, I personally wouldn't make the efficiency at high temperatures the deciding factor in deciding on the most suitable panel - the difference you notice will likely be minimal.

Connecting solar panel into domestic electrical circuit

2008-01-30T15:51:00.001Z

If I bought a solar panel to take abroad could I link it up directly to the
house electricity cables after the voltage meter?
Would this draw less power from the grid during the day?
Kindest regards, Saiduz.

Unfortunately it's not that simple! Solar panels produce DC electricity, usually at 12 volts, which is fine for battery charging. But it's not compatible with 240 volt AC mains electricity. You can use an inverter (eg the Silverline Inverters or Steca Inverters on our website) to produce mains electricity from the battery that you have charged, but even then you can't simply plug that electricity straight into your mains circuit, as the frequencies they are running at will be slightly different and out of phase. Any equipment running off the inverter would have to be on a completely seperate circuit.

It is possible to get a type of inverter which can connect into your mains electricity. However these 'grid-connect' inverters are far more expensive, and only really suited to big arrays of solar panels.

How many solar panels to get 5kWh per day?

2008-01-15T14:16:00.001Z

I am interested to find out more about calculating the amount of PV panels for my usage. It is around 1300KW a year with peaks around 5/6 a day. Is there a calculator that I could use to sort out what I would need?

Also are there any solar hot water panel and tank size calculations online?

many thanks, Tom

Hi Tom,

Have you looked at our solar panel calculator?

If you already know your energy usage you can skip the first couple of sections and go straight to part 3. If you put in 1000W of solar panels it will give you a rough idea of what you can expect from them per day: about 5000Wh (or 5kWh) in summer; 1000Wh (1kWh) in winter.

So, to get about 5 or 6 kWh in winter you would be looking at about 5000-6000 watts of panels. But it would be much easier in summer - you'd get the same return from just over 1000 W of panels.

Sorry, I don't know of a similar calculator for solar hot water systems.

Can I use a solar regulator to regulate a wind turbine?

2008-01-11T17:42:00.001Z

Just having a look on your website for wind turbines and regulators etc. You suggest that you can connect up to 100W of solar panels into the wind turbine regulator in addition to the turbine itself.

Does this work the other way? ie. Can I plug a wind turbine into the solar regulator I already have?

I'm fairly sure the answer to this is no, from my memory of wind turbines they actually produce AC voltage by induction, is this still the case or do they now produce DC voltage direct?

Yours realising just how long ago it was that I last looked at electronics!!!

Neil

Hi Neil,

You're right that it's not a good idea using a solar regulator for a wind turbine - but it's for slightly more complicated reasons! Yes, turbines do produce AC by induction, although in fact it's normally rectified in the turbine itself so it's usually unsmoothed DC that comes down the wires. The problem is more to do with what happens when a regulator senses a battery is full. Most solar regulators will simply open circuit, which is fine for a solar panel. But an open-circuited wind turbine will spin freely, which is bad news in strong winds. So a turbine regulator is usually designed to short-circuit the turbine, which slows the blades down.

Also, solar regulators might not like the relatively spiky DC from the turbine compared to the very smooth DC from a solar panel.

Having said all that, you might get away with it in places that aren't too windy - but it's not really recommended by the professionals! You are likely to shorten the lifetime of your wind turbine.

Heating a garage by solar power?

2008-01-03T12:11:00.001Z

I live in west wales and run on heating oil. Can you give me all the relevant info on solar for my home hot water systems and also electric systems.
Would the sticky panels work on a conservatory?
Also if I wanted to use a solar panel to give a large double garage heating would this work if the garage was in constant use?
Glynne.

Hi Glynne,

The flexible adhesive-backed panels should work on most surfaces which are big enough and flat enough - note that they are 3 metres long though, and they would probably not go over ridges very well, so it depends on the surface of your conservatory roof. To get the best results from solar panels it is important that they are angled south too, to get the most sunlight.

Note too that panels produce DC electricity, so you have two options - either use them to charge a battery, and run DC lights etc off that, or buy a grid-connect inverter, which allows you to connect the system into the national grid.

Hot water solar panels are generally used just for heating water for domestic use (washing, showers etc.) They aren't really a replacement for space heating, so no, I'm afraid you couldn't use them to heat your garage. The reason is that you get no output from your solar panels in the middle of cold dark winter nights - which is when you need the heating the most! For more information on solar hot water panels I'd recommend you try Navitron (www.navitron.org.uk).

Integrating solar into existing power systems

2007-12-28T17:49:00.001Z

I am currently looking into the feasibility of all forms of renewables as a supplement to existing power supplies. I have had a number of amorphous PV panels on test for six months with a quite small load. Any thoughts on how to integrate a small scale system for lighting(using LED lamps) would be appreciated ! Simon.

Hi Simon,

When you mention 'existing power supplies' do you mean mains electricity or a battery powered system? The two are fundamentally different. To integrate solar panels into a battery system is trivial - simply connect the panels into the system via a regulator.

For mains supplies, integrating is harder. You can get inverters to convert the DC electricity from the panels into 240VAC to connect to the national grid, but they are not cheap, and it's not DIY wiring! For a small scale system of less than a few hundred watts it's not worth the effort and the cost. Besides, LED lights are usually low voltage DC types, so converting from DC to AC and back again is a bit pointless.

An alternative is to run the lights from a switch that can be set to either 1) a battery bank that is charged by solar panels or 2) a mains-powered 12V power supply. Most of the time you can run the lights off your batteries, but when they begin to get low, simply switch over to the mains supply. It wouldn't be terribly hard to create a circuit to do it automatically when the voltage began to drop.

A friend of mine runs the lighting in his kitchen from such a setup, and it has worked very well for him.

Solar panels for Antarctic expedition

2007-12-27T19:27:00.001Z

I am starting to make enquiries about solar power for a proposed antactic expedition in 2009/10. I would be after lightweight panels that could be put over tents or the sledges to charge sat phones etc.

Please let me know if there is anything you can offer that may be suitable.

Yours, Chris

Hi Chris,

Unisolar used to make some excellent flexible panels that were ideal for strapping to tents and sledges, and performed very well. Unfortunately they are out of production at the moment, but if they come back into production in the next few months (as I understand Unisolar are planning) they would be the best ones to go for.

There is a similar flexible solar panel from Powerfilm, although a friend who used one in the Antarctic last year was a little disappointed with the output.

I would however recommend the Spectra solar panels as a good solution. Although not flexible, they are very slim, have grommet holes in the corner so are easily lashed to sledges and tents, and are very lightweight (and good value). We sell 5W, 10W, and 20W models - see http://midsummerenergy.co.uk/buy_solar_panels/spectra_marine_solar_panels.html for details.

Best wishes for the expedition anyway! As it happens I'm off to Antarctica myself for a couple of months shortly - it's a fantastic place to spend some time!

Solar power for narrowboat

2007-12-27T18:59:00.001Z

hi
What would you recomend as a wind and solar system for our narrowboat? It will be for liveaboard, battery bank is 600amp, running lights and 12v fridge, 12v tv, dvd, and usual waterpump/shower emptying pump.
regards
bob

Hi Bob,

If you are running a fridge you need a fair area of solar panels to make a difference, even in the summer. I would recommend a minimum of 2 panels of around 60 watts or so. By far the neatest solutions are the adhesive backed 'peel and stick' Unisolar panels. You should probably go for the kit option which includes the most appropriate regulator - click on 'solar panel kits' in the shop menu.

The advantage of the adhesive-backed panels is that they are very low-profile and simple to install. However, because they are flat on the roof they won't be quite as efficient as a framed panel which can be tilted towards the sun. The Unisolar ES62 panels are a very good value alternative if you want to go for framed panels.

Wind power is useful in the winter when you get less from solar. Be aware though that the output from a wind turbine does depend very markedly on your location - if you are surrounded by trees or buildings the amount of power can be a bit disappointing! However, they can give very useful power in locations which are more exposed. Again, as you are running a fridge, which is quite power hungry, you would be looking at the larger of the models we supply, the Rutland 913. You would also need the HRS913 regulator to connect it into your batteries.

Tristar regulator and battery monitors

2007-12-27T14:03:00.001Z

We have just installed 7 x170w 34v solar panels and we need a regulator. Would the Tristar TS 60 be too big? Also we have two other regulators for other panels - is there a monitor into which we can feed all the solar info to give us one lot of information on charging, battery status in % or amp hrs?
Sally

Hi Sally,
I'm slightly confused - 34V is an unusual voltage for a battery-powered system! Big panels such as those are usually used for grid-connected systems, where you produce 240V AC (domestic electricity). In those cases you wouldn't use a regulator such as the Tristar; instead you would use an inverter.
If you have a battery system, it would usually work at 12 or 24V DC. If it's a 12V system, your panels are really producing too high a voltage. But, if what you have quoted is the maximum voltage (usually given as 'Vmax'), they are about right for a 24V system. You have a total power of 1190 W (7 x 170), which at 24V is still a bit under 60 Amps. So yes, if you are running a 24V system, the Tristar 60 would be perfect.
You can get battery monitors to give you the state of charge of your batteries. For 12V systems the NASA BM-1 is very good (http://www.nasamarine.com/). I think Steca make a similar instrument for 24V systems - if that is of interest I can get you more details. At the moment we don't stock them, but we may be able to get one in.

Solar power in Bangladesh

2007-12-25T15:56:00.001Z

Hello there, I'm interested in setting up a small kit in Bangladesh as the sun is strong and plentifull as a trial to test it's usefullness. I'm unsure what to try as a starter. Can you suggest something please for me?

Many thanks
Kind regards
Saiduz

Hi Saiduz,

Bangladesh would certainly be a good place for solar power!

It depends what you want to power from the panel. I would suggest the smallest setup that would be of much use would be a Spectra 20W solar panel, with a Morningstar Sunguard regulator; you would attach that to a 12V lead-acid battery (which I'm sure would be available locally). That wouldn't give a great deal of power, but perhaps enough to run a radio and a fluorescent light or two in the evenings. However, it would give you an idea of what could be achieved with a larger setup.

Solar panels for kayaking expedition

2007-12-25T15:53:00.001Z

I need a panel capable of charging video camera batteries, mobile, and laptop for a three month solo kayaking expedition. What sort, how many, what price?? Thanks.

Sounds like a fun expedition! It would be worth you working out fairly carefully how much power you need. If you use the solar panel calculator on my site ( http://midsummerenergy.co.uk/solar_panel_information/solar_panel_calculator.html) you can enter the power each item consumes, and how many hours you need it for each day. A laptop for example might be something like 100W, but only for 1 hour a day on average.

That will give you a good idea of how big a solar panel you need. I would guess though that you might be looking at something like a 20W panel. The Spectra range are pretty good ( http://midsummerenergy.co.uk/buy_solar_panels/spectra_marine_solar_panels.html), although I would perhaps go for 2 x 10W (£92 each) rather than a 20W as they would pack away smaller. They are light and reliable though, so would make a good choice. If you find your needs aren't that great, you might be able to go down to 2 x 5W panels instead.

I can also get in some Unisolar folding panels which pack very small and are designed for expedition use. They are considerably more expensive though! See http://www.uni-solar.com/ , then follow links to 'Standard products' and then 'Portable modules'.

Whichever you go for, you would also need a battery and regulator. The Sunguard regulator (£26) is small, waterproof, and ideal for panels up to 50W. A small sealed lead acid battery will be the heaviest part of your kit.

Hope that helps.