Solar powered generator is a serious project, big or small, for anyone who is able with his hands, and has at least a full high school background in physics; that includes most chiropractors.
"With the world's population expected to grow by one third to more than nine billion by the year 2050, the world will need
- United Nations
If I was to do it all again, I'd try and build my panels on the ground like these that I spied in a small fishing village in Holland; but they are in morning shade.
Perhaps the very best option is to contsruct a new workshop, its roof dedicated to your solar powered generator; 60% of the panels would be facing due south (in the Northern hemisphere, angled at your latitude), with 20% east facing at 60 degrees to catch the morning sun, and another 20% west facing. The home's greatest electrical needs are not at midday.
As you will read below this building of a solar farm has become something of a saga; never did I realise how I would fall in love with free energy from the sun. If I was you, if you can afford it, go big from the beginning. I wish I had. I've yet to meet anyone satisfied with a Mickey Mouse solar powered generator.
I've just increased my solar residential panels by adding four more larger PVs, 185W each, two more batteries and upgraded to a 5 kilowatt inverter. Now we should never need grid electricity for our basic needs.
Now I'm about to add yet four more 235 watt panels but it makes for complications. Go as big as you can afford from the beginning, and use the same size PVs if possible.
There are any number of reasons why you might want to go for home solar power. Perhaps it's a consuming passion for the environment, and most sources of energy are provided from dirty fuels like coal, uranium and oil.
Or perhaps, like me, you live in an area where the electricity is increasing unreliable. Sudden unexpected losses from the grid do interesting things to computers and a solar generator, for one, provides a reliable uninterrupted power supply.
Sudden losses of electricity can also be very distressing for the home and business. We started regularly losing mains power when the bread machine was busy and she who must be obeyed would fume; no loaf today and a wasted lump of dough. That's small beer compared to the effect on industry; everywhere people are buying petrol driven generators but, for my money, use of Mr Golden Sun is a better option for many.
Total blackout is now a serious possibility in South Africa; it would apparently take two whole weeks to reboot the grid from a so called cold start.
If I was to build another solar powered generator, knowing what I know now, I wouldn't put it on the roof. Why, you may very well ask? That's the way everyone does it; true but at residential solar panels pitch you'll find there's a better way.
Or, whilst I was in the midst of treating patients, loss of power would render my chiropractic table useless; then it was my turn to sulk.
I've just lost a whole hour's work whilst building a page for this site on lettuce wraps recipes when the mains tripped; yes, serves me right, I hear you saying. I should save my work more frequently but sometimes one becomes engrossed; in future this computer will be working only off solar. Even with the odd cloudy day the sun is more reliable than our electrical utility.
No matter how limited your physics background, you probably have a vague idea that the sun radiates the earth with energy. These joules come in small bundles called photons; they have a wave pattern with different frequencies.
Some is in the light frequency range, and other in the infrared spectrum which can be used to heat water, for example; also ultra violet that damages the skin and even more toxic x and gamma rays in small quantities.
Most of this energy is used by plants to convert solar by a process called photosynthesis into usable energy in the plant; hence the global concern at deforestation and the loss of plant species.
Loss of power for eight hours last Christmas eve was the final straw.
We made the decision to change over to gas cooking and home solar power
for fridge, computers and lights. Even the solar electric oven, which draws only 2.5kW can be connected to the inverter, using a change over switch; that allows you to simply toggle back and forth from the utility.
So, how does solar energy work?
Radio waves on the left have low energy (frequency) but gamma ray photons are very destructive having a high frequency (low wavelength) causing many of the genetic mutations that are so prevalent.
Most of these waves will activate your solar panels, but the infrared portion (the heat photons) are filtered out by cloud. But even on a cloudy day, quite a lot of photons will get through and activate the solar panels.
Your home solar power programme should first and foremost be to capture the infrared (heat) part of the spectrum. Providing free hot water is the most effective (and cheapest) way to capturesolar power energy. It contributes about half of your home carbon footprint.
Now to the main part of this page at Bernard Preston dot com; building your own solar powered generator. Firstly, make sure you understand the process; really it's not rocket science. Walk with me, step by step, and you'll get it. Along the way, expect to ask your kid some questions about watts, or the formula for heat losses in a wire, and so on.
Two roads lead to the solar utopia.
You can go about building a solar powered generator in two ways, depending on your interest, knowledge and skills. Firstly you can pay someone a lot of money to set it all up for you. There are electrical engineers and electricians who will do it do it very effectively and properly but, as always, do your homework; shop around and talk to people.
Secondly, you could build your own solar generator yourself. You'll save a lot of money and have a lot of fun but, if you don't do it properly, you could electrocute yourself.
It's been said many times that an amateur with the will to learn and work can build a house. But it takes a professional to build a bridge across the highway. Building your own solar powered generator falls somewhere in between. You could do it. I did with only a little background, but you do have to learn about the process first.
The first rule is to start as big as you can afford from the beginning.
You can build a small, relatively inexpensive solar powered generator that will just power your lights and computers. But if my experience is anything to go by, once hooked on solar home power, and all that free energy coming from the sun, you'll start thinking. What about the fridge? Could I power an electric drill and the vacuum cleaner? What about the bread maker, the coffee machine and the induction cooktop stoves?
Even a hot water kettles and modern ovens draw about two kilowatts which is not beyond a five kilowatt inverter. But the hob should be gas and your hot water geyser should be energised by solar tubes rather than solar photo voltaic panels.
Here's an update, however. There are now hot water geysers on the market that can be powered directly by photovoltaic panels. It's done using induction, and requires less than half the electricity of the conventional way.
Also, clouds readily block off the infrared heat, but far more light energy gets through; they are more effective on cloudy days than vacuum tubes.
The two parts that are not easy to change are the regulator, known as a maximum power point tracker, and the inverter.
More about what they are, and what their functions are later but, at the very initial stage, go as big as you can afford; upgrading later is a costly business.
Consider also a grid tied inverter which enables you to sell your excess power to your utility provider; if they will buy it. They are getting more sticky about it.
My thoughts are to go at least for a sixty amp regulator and a five
kilowatt inverter if you can possibly afford it. You can always add more
panels, but upgrading these two babies is an expensive business. If you
go big in the beginning, it hurts only once.
So, here's the deal.
There are electrical losses in all conducting cables; some of your solar power is lost as heat; it's inevitable but, to minimise these lost watts, you want to have your photovoltaic panels as close to the regulator as possible.
How close should that be? Well that depends on how thick your cabling is, and how high the voltage from your photovoltaic panels. Of course it's also determined by which area of your roof receives the most sunshine, and particularly early morning sun. If your voltage is 100V or more, don't get too phased about those losses.
I started with six small 16 volt panels in series totally about one hundred volts. That cable needs to be quite thick; I am using 10mm cabling in our home because the distance has to be greater than normal in our situation; about 25m. Nearer to the regulator the roof is in shadow from large trees for quite long periods in the morning in winter.
In the end, it's worth buying as thick a cable for your solar powered generator as you can afford. It's a once off cost and will minimise your losses.
The maximum power point tracker is a regulator that prevents batteries from being overcharged and damaged; a vital part of your solar powered generator. The function of the MPPT is also to change the incoming voltage from the PVs to that of your batteries and, when they are fully charged, to turn off the incoming power; it tracks and maximises your panels, increasing their efficiency by at least a third; you can't do without it.
If you go away on holiday for a week, without a regulator, your batteries would be cooked when you got back; a vital piece of the equipment.
Your car has one too to protect the battery from being overcharged by the alternator.
talk more about the controller on another page later, but go as big as
you can. I started with a 20 amp regulator, and soon realised it was too
small for my newly ambitious needs, and upgraded at considerable cost
to a 60A MPPT. And I'm now thinking perhaps I should have gone bigger
still! But do yourself a favour. Don't go less than 60A, except for a
very specific purpose; for example I knew I wasn't going to add more
west facing solar panels; the 20A MPPT was adequate.
In fact, rather than going to a 100A maximum power point tracking device, the advice I've received is to install two separate 60 amp MPPTs. Since adding the west facing solar panels, that's what I've done; the latter has been less effective than I'd hoped.
Another reason is that clouds cause a solar lens effect which can temporarily increase the amps by as much as 50%.
Depending on various factors that we'll discuss later, the regulator will reduce the voltage from your array of PV, and simultaneously increase the amps. The current.
I have six PVs in series (we'll talk later about series and parallel linking of batteries and PVs, relax!) each providing about 16V, around 100V in total. The regulator must step that down to the voltage of your batteries, 24V in my case.
This MPPT will handle up to 150V. So, my six panels provide around 100V, but, if it's a bright, mid-summer's day, and the batteries are fully charged, the incoming voltage will surge to around 123V. So, I could put a seventh 16V panel in series, but more would go periodically over 150V and cook the MPPT. Talk to your supplier.
Upgrade: Since the upgrade to a 48V inverter, it's interesting that the MPPT can extract more energy from the photo voltaic panels. On the 24V system, the energy supplied by the panels was 400-500W. Now the energy supplied goes over 600W. Ad nauseum, I repeat, go as big as you can from the start. Everything is more efficient. And more costly, but worth it in the long run.
A bit of simple physics to fully understand C
Power (measured in watts) = volts x amps (or VA)
Say my PV panels are providing on one sunny day 400 watts of of direct current power, at 100V and 4A. This energy is travelling along the copper cables to the regulator, but the regulator must now drop the voltage down to that of the batteries (24V). About a quarter. So, the regulator will turn that 400W (at 100V and 4A) into 400W of still direct current (DC) at 24V and about 16A.
The voltage drops by a quarter, the amperage goes up four times, but the watts remain the same at 400 watts of power being provided from the PV.
You may say, so what, do I really need to know this? Yes! Why? Later, when we talk about losses in energy along the pathway, we'll see that the losses are dependent on the current (amps), but not the voltage.
So, there are big losses in that cabling between the regulator and the batteries, because of the very high current, so those cables must be as short as possible, less than a metre, and as thick as possible.
Got it? The cables at C (refer to the diagram above) must be SHORT AND THICK. Because the current is high and we want to minimise the losses (as heat) in the cabling.
Minimising the losses in your solar powered generator is absolutely vital. They can be very significant, and demoralising, but it need not be so if you follow these guidelines.
The energy losses in the cables follow the formula:
Joule's first law:
Heat generated = (amps) squared x (resistance) x (time)
So keeping the amps and the resistance of the wires low is vital; and especially the current, since it's squared.
How do you keep the amps low?
Surely you want as much current as possible! Nope. You want as much power (watts, remember) as possible. And since Power = (amps) x (volts), if you raise the voltage at A as high as possible, then you can have low current (amps) and still oodles of watts.
PVs in series for your solar powered generator
Like I said we'll discuss series and parallel later, but simply put, if you put a number of PVs in series, the voltage is additive. More panels, higher voltage, lower current, less losses.
I have six 18V panels in series for my solar powered generator, and now in the upgrade another four 28V panels. So they provide a voltage of about 18 x 6 ± 112V. It varies. Right now some very high cirrus is creeping across the sky (rain tomorrow), it's 15.00 so the voltage and watts are dropping. 180W, 90V and 2A to be precise. I've just checked! To be sure the batteries are full tonight, I've just moved the fridge back to the grid. A more sophisticated system will do this automatically. More about that later, too.
At noon, the power was over 400W, the voltage around 105V providing around 4A. Still high voltage, low amperage, exactly what we want. (Since the upgrade with the second string of panels, there's figures have increased, but the principle remains the same. High voltage and lower current.
Understanding how diodes work is important if you have different panels in your solar powered generator.
Tip: PV's are getting bigger and bigger, and the cost per kW is coming down. Buy the biggest panels you can, and ask if they'll still be available in one year. If you want to upgrade, and they have a different voltage (likely, since the PVs are sourced from all over the world. My first were from South Africa, then German PV's were cheaper, now the new 235W are from Canada!)
So you will need a stud diode to prevent one panel forcing the current backwards in one of the other strings. How diodes work will help you understand this; perhaps not included in high school physics.
Sometimes on a small system powering say a 12V gate motor, you may decide not to use a regulator; there's always the danger of overcharging your battery. Here's a different take on how diodes work.
In many developed countries, where the power supply is reliable and clean (having neither voltage spikes nor brown outs - drop in voltage - which can seriously affect the electric motors such as needed to drive your fridge) your solar powered generator is able to transfer any surplus energy back into the grid. Basically, it turns your meter backwards.
However, in South Africa, it's not legal, though I believe some people do it anyway. The problem being that, if the power is off for maintenance, you may electrocute a technician unless you have a dinkum grid tied inverter.
The big advantage: no batteries to store your power.
A big disadvantage: The downside is that you cannot draw power from your own generator, even if the sun is shining, if the grid goes down.
A city electrical engineer tells me that grid tied inverters are causing huge problems world wide. Already some states in the USA have banned pumping your surplus back into the grid; my manual generator is the perfect compromise.
The other problem, as in South Africa, is that the grid may pump dirty electricity back into your pump damaging your equipment; personally I've decided to build a manual system, but still have access to the grid, but they are quite separate.
One of your first considerations is whether to construct a manual or fully automated system. The Solar manual automated debate must be faced.
Fortunately it's coming at a time when huge investment in battery research for electrical cars is making having your own storage for your surplus electrical power a realistic cost effective proposition. The whole scene at solar powered generators is in flux; it's an exciting time.
Right, the high voltage / low amperage direct current (DC), has arrived at your MPPT which has stepped down the voltage to that of your batteries. The MPPT does it automatically, regardless of whether you have a single 12V battery, two 12V batteries in series (24V), or a 48V system.
Remember, power = volts x amps. If the voltage has dropped, then the current has surged by an equivalent amount, and that means big losses in Step C. Heat losses = current x (resistance) squared.
The solution: the cable between the MPPT and your batteries must be short (less than a metre) and very thick. Basically the heavy duty cables used in your car to and from the battery. For my solar powered generator, I'm using 50mm red cable, but I'm told it's overkill; you can't go to thick and the increased cost is minimal.
Here I confess I have no expertise, and I recommend you talk to as many local people as possible. Two strong suggestions:
The batteries are a large part of the expense of your solar powered generator. Hence, if you can "grid-tie", and not have batteries, it will reduce your costs significantly. However, that won't do in South Africa with frequent outages and surges.
Buy the best batteries you can afford. Gel cell, lead crystal and there are a heap of others on the market. It's worth it in the long run.
And even if you have gel cell batteries which in theory you can drain down to zero, try not to go below 50%. You will shorten their lives, though far less seriously than ordinary car batteries.
As you will have realised by now, the losses in the cabling is directly related to the current, not the voltage. Having a high voltage system (24V or 48V) is preferable. That means you would put two or four 12V batteries in series.
These are sealed "lead-crystal" 205Ahr batteries; they are very heavy, and damnably expensive, but are supposed to last 7-12 years. We'll see; they are now five years old, and still perform perfectly. Get help moving them, or you will soon fall into the clutches of your local chiropractor, and I'll be accused of drumming up work for him/her!
It's now five years down the line and my batteries are still not showing any signs of aging; in fact I've just done an upgrade to four more batteries in parallel.
I wish I'd been compelled to face the 12-24-or-48V solar generator question from the start. Do yourself a big favour; go for 48V despite the fact that you must have at least four expensive batteries, rather than the Mickey Mouse two you can see below; you won't be sorry. If you don't you'll be making an unnecessarily expensive upgrade in a year or two.
Safety: Having large batteries and cables exposed like this is very dangerous if you have prying fingers around. I've now finished building the stairs in our new home, and the space underneath makes the perfect secure, cool, resting place for your solar powered generator. Keep the door locked, if you have little mites running about.
It should have a smoke detector and a fire extinguisher. Now I'm considering a knife fuse to isolate the batteries in the case of a short circuit.
The knife fuse is purchased, but not yet installed. I've chosen a 125A model which limits the batteries to
48V x 125A = 6 kW
Although the inverter will deliver 10kW we simply don't need that amount of power at any one time; so I'm being conservative. It's not an expensive device and it would be simple to increase the fuse to 160A for a few dollars.
Step D @ Solar powered generator
Right, so now your solar energy has been successfully stored in two or more batteries. This is a 24V system, with two 12V batteries in series.
Step D is the passage of 24V, high amperage direct current (DC) from where it has been stored in your batteries to the inverter.
Again, short, thick cables.
Upgrade: I've just upgraded by adding two more batteries to a 48V system, and a 5kW inverter. I should have done it in the beginning. Getting free energy from the sun is addictive, and like chocolate you just want more and more.
I've just checked: we've used 207KWh from the grid in four and a half months since installing our basic system. Now, with four more panels and the new batteries and inverter, it'll be even less. In fact, I'm hoping almost zero. Just my large thicknesser-planar needs a huge amount of energy. And even that might cope, if we turn everything else off. One doesn't want to stress your system, using it near the limits. The solar electric oven is no sweat for a big inverter. Go big as you can avoid from the start; then you can avoid the mistake I made and the need to be making a solar powered generator upgrade.
Aside: You may find this boring, if you have a physics background, but it's a common misconception. Since upgrading from a 24V to a 48V inverter, with four 12V batteries in series, it's noteworthy that the meter shows the current has halved. Double the voltage, half the current, half the heat losses.
Your inverter is the heart of your solar powered generator. It has one very important function, viz, to turn your 24V direct current into 220V alternating current (in SA), and 110V in the USA and Canada.
Now you can use that solar energy to light your house, run your computers and TV, the fridge, all electric motors. We use it to make coffee and power the bread maker, but only on sunny days because heating uses a lot of energy.
It's an expensive part of your solar powered generator, and I strongly recommend you purchase the best possible quality, with lightning protection and as large as you can. At least 2kW, and I'm ruing the day I didn't spend the extra and purchase a 5kW or even 10kW inverter from the start.
We started thinking we would only want solar power for lights and computers when there was a power outage, but quite soon we got hooked. And want to power far more appliances.
Don't buy less than 2kW and, if you can afford it, buy yourself a Christmas present and get a 5kw inverter. Or 10kW. The price goes up... but it's a good deal less than wanting to trade your current inverter in for a larger model. Do it right the first time. I'm sorry I didn't.
There are many items, like your hot-water kettle that use around 2kW. A 2kW inverter just isn't adequate for that. Also, electric motors draw a high current for a short time as you turn them on. Bingo, your inverter switches off automatically to protect itself.
So, my advice, a 5kW inverter and, if you have the money, a 10kW. I've just decided to upgrade to 5kW and should have bought the bigger one in the beginning. The 10kW is more than I need.
If you live in South Africa, I can seriously recommend these MicroCare inverters; plus their customer care is impeccable.
When I started building my solar powered generator MicroCare were not yet making grid tied inverters. If were starting now, I would consider it; they enable you to return your excess power to the grid. It would turn the meter backwards, reducing your overall power consumption from the grid; there are big down sides though if you have a dirty grid. I haven't done it, and won't be.
Your appliances cannot be simultaneously powered by solar and mains. You will need a change over switch with a neutral between the sources of power; this saves a lot of hassle.
There's only one option if you are going to build a solar powered generator, and that's to buy LED light bulbs. Light Emitting Diodes. But it's a step you should be taking anyway. Very soon you will not be able to purchase incandescent globes. They use far too much energy and have a limited life span.
Do NOT get into CF globes. Compact Fluorescent. They do use much less energy than incandescent, about three times that of LEDs, but they contain very toxic mercury (and break very easily in your fingers whilst fitting them), and new research is coming out about skin cancer from their light.
Pay the extra, and buy LED. They are reputed to last 15-30 years, though who can confirm that. On a high quality, clean electricity, system they should last indefinitely. But if you have dirty spikes in voltage like we have in South Africa ... nothing will last. It's one more good reason to go solar. Rather spend good money on getting clean energy from the sun, than bad money buying a new TV, fridge... because of dirty electricity.
This light fitting above my computer will take three globes. But it's so bright that I've fitted only two 3W globes, one yellow and the other bright white I've pointed to the ceiling. It's far too bright pointing straight down. 6W providing more light than a 60W incandescent globe; it's the future.
But beware. LED light is different; brighter, harsher. You have to get used to it, use different light fittings, especially those with a lamp shade; soft white is available.
Bernard Preston has had a lot of fun building this solar powered generator; it's an hour before dawn and I'm typing this using the sun's energy stored in batteries, regulated using maximum power point tracking, inverted and turned into 220V alternating current electricity. 110V options exist too obviously.
You must know some basic physics including how diodes work; it's not rocket science but grasping the fundamentals before making a start is vital.
Bernard Preston is an Apple fan for numerous reasons, but not least because they use less than half the energy of a PC. Steve Jobs was adamant becuase of the noise the fan makes; it did mean the early Apples overheated. Roughly 150W vs 350W; anyone using a solar powered generator has to look at ways of using devices that draw less current, especially at night when there's no incoming solar power.
If you also have a wind turbine or a hydroelectric device, that's another matter. Bernard Preston has neither.
And so you can use your Solar powered generator to power any number of appliances, especially when the sun is bright. We run the fridge, two in fact, the washing machine on cold wash, and the dish washer using hot water from the Solar geyser. More about that on another page, but just to say, the water temperature is extremely hot, 80 degrees C and more on a bright summer's day, from the solar geyser.
Less than sixty kilowatt hours per month using a solar powered generator
It may seem unbelievable, I can hardly believe it, but we have used less than one hundred kWh of energy in three months from the grid. All the rest comes from the sun.
Update: Then came Christmas, turkey, Christmas cakes, a ham... we seem to be averaging out at 45-50kWh per month.
But yes, we are careful. You don't leave the TV on all day, you put your computer to sleep when not in use, and the iron? Well, that was ditched an age ago. A wood stove for heating, a gas stove for cooking, solar energy for hot water, and no air con.
Good luck, have lots of fun. I have. Except for climbing around in the ceiling putting in new cables. That wasn't fun!
How does solar energy work? Like a bomb. Fantastic.
Installation of the panels
If you possibly can, build your arrays of solar panels on the ground where it's easy to adjust them for summer and winter but often this is impossible in a built up area because of limited space and shading. Installation of PV panels for your solar generator isn't really difficult, if you have two right hands.
One new development is the thought that we should have at least some of them pointing west; they will be less efficient, but provide energy in the later afternoon when we need it most, and some east facing solar panels too for your early morning coffee.
Going solar, going green, why do you want to do it? Just how passionate are you about it?
You need consistently strong winds to make a wind turbine effective. In our area they are a dead loss. I have no experience of them, so look elsewhere, I'm afraid.
The cost of a Solar Powered Generator?
I'm sure it varies enormously depending on where you live, and who you deal with. To date I've spent about $4000 but a third of that is for the batteries. But I'm about to add considerably to that to upgrade my solar powered generator to 48V, an extra 500W of panels and a 5kW inverter.
Upgrade: the new 5kw inverter (an extra R6,000) and two new gel 100Ah batteries (R10,000 a very big expense) and four 185W panels (R2,000) have added another $2200 to the price of our solar powered generator.
Say, around $6500 once you've added in cables and assorted bits and pieces. We could now probably go off the grid. What's your monthly electric bill? Electricity has gone up by 25% per year for the last five years in SA, and projected at another 16% year for the next five years. Our solar power energy investment will pay for itself in five to seven years. But then, this is sunny South Africa! Live in Arizona? Perfect for home solar power.
I'm sure you could spend double that, and more, to have a professional design and fit your system. Don't do it yourself unless you are serious about learning the basics, talking to people, reading, studying, and bending your back, whilst crawling around in the ceiling. Seriously, you can electrocute yourself and destroy the expensive components. To date, I'm alive and well and having a ball building this solar powered generator!
Update: It's now 15 months since I installed this Solar powered generator (myself) and if anything, I'm even more enthusiastic. Such that I'm planning another 4 x 185W panels. I'll admit, it's pure greed. I just love getting a free gift. Even from Mr Golden Sun. You could too.
A big new advancement in the home are the induction cooktop stoves, kettle and geyser.
These are all items that need replacing periodically in the home; they use less than half the energy and provide heat at twice the speed; instant heat, like gas, at the stove is a joy. Also the stove top doesn't get hot; I've just bought our second induction cooktop stove plate. They are dropping in price as they become more popular. I paid only $40 for it and it provides 2kW of instant heat. They only work with iron or steel bottomed pots.
Going solar gets you into a lot of new innovations too; it's just one thing that gets me excited about a home solar powered generator.
Plants of course can trap the sun's energy a lot more effectively than we can with our photo voltaic panels; they are little solar powered generators! And then they make that food available to us. Those lettuce wraps recipes; it's so easy to grow greens, and deliciously fresh straight from the organic garden.
This is all about our philosophy of backyard permaculuture; working with nature, rather than against it when you never can win in the long run; the hand that feeds us will bite us back if we abuse her.
Solar power energy
» Solar powered generator
The regulator is on the right.
Heating water takes up fifty percent of your electricity.
Light emitting diode lamps are a must.