I have been thinking a bit about how best to orient solar arrays lately. I know that the optimum angle (for maximum total energy generation per year) is quite low, because most of the energy arrives in the summer, but if you want to get consistent power year round then a steeper angle is desirable, to maximise the slender solar in winter. There are also issues around shedding snow in some places (steeper is better) and around making best use of bright diffuse cloudy light (lower angle is better for places that do not see much sun at all).
I had read that it makes sense to split the array and put one part facing east and another facing west (some buildings force you to do this) and in the end you can get almost as much energy per day that way, losing maybe 15% compared with a south-facing array. The east array works well in the morning and the west works well in the evening and so you get more consistent power output without the high peak in the middle of the day, which is likely to be more than your battery can actually absorb in some cases.
So that started me thinking about lead acid batteries and how you charge them and I realised that they take a lot of charge at first, but later in the day they need less because they have arrived at the absorption voltage and the current tapers downward during the absorption phase. During this downward taper, the charge controller is rejecting much of the solar power so it is effectively irrelevant whether your array can produce high power output (unless you have a diversion load such as water heating off the surplus solar which everyone should have but very few actually seem to bother with).
So the logic took me to a conclusion that I have not heard or seen before surprisingly and I thought I’d share it here. If you face your array south east then you can get about 50% higher power in the morning, thus getting the battery charged quicker. Having reached the absorption voltage in the middle of the day, the array needs less power in the afternoon so it does not matter that this is less than you could have had available using a south facing array.
Here are some charts of solar power availability hour-by-hour to 2 arrays sited where I live, one facing south and the other south east (each at 45 degree angle) showing how the available power varies over the hours of the day in each month of the year. I got this data from https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html The red curve is south facing and the blue one is the south east facing array.
It may not look like it, but the blue curve is about 50% higher power than the red one in the mornings which I reckon will bring the battery up to its absorption voltage quicker and allow it to absorb more power in the course of a day than it could with the red curve, even though the red curve offers more energy overall. That’s because you can’t actually use that extra afternoon energy to charge a lead acid battery because it cannot absorb power at such a high rate during the latter part of the charging cycle.
PowerSpout plan to increase prices of their hydro turbines and associated gear by approximately 15% on 1st April. This will be the first rise in several years. At present exchange rates, a turbine costs approximately £1190 with an additional £150 shipping cost from NZ. Often you can add a few items to your order and get free shipping.
To accept an order we need some detailed site information. I can help you with this and with the details of your hydro system design and let you know if it’s going to be worth doing or not. I spend much of my life these days chatting with people on email or phone to sort these things out and it’s a fascinating task. So feel free to get in touch if you are interested and you have a site in mind.
You can also use the PowerSpout drop down menu above to access more info and reading matter.
Recently I have written two new reports about small PM-generators which make use of the housing of an asynchronous motor frame size 80 and four neodymium magnets size 80 * 20 * 10 mm. Report KD 681 describes an 8-pole PM-generator which needs a rather simple 8-pole, 2-layers winding. Report KD 683 describes a 4-pole PM-generator for which the standard 230/400 V winding can be used. Both reports are added to my website www.kdwindturbines.nl at the menu KD-reports and can be copied for free.
It would be nice if you add this message to your blog.
Greg sent me some photos of the hydros he is building using axial flux alternators to provide direct single-phase AC for sites in Papua, Indonesia. Here is some information. Greg’s email is [email protected]
These are single phase units, 240VAC, 50Hz.
The first model (I made 6 units about 6 years ago) had magnets secured with a Stainless steel band and fibreglass epoxy. magnets are 60mm diameter. It is capable of up to 2.8kW (1000RPM). Measured efficiency was around 93%.
I started on 18 “Mark 2 machines” about 4 years ago, but life intervened and they have been on hold since. I’d be happy make a little report with a few more details if you think people would be interested.
The second model is still under construction, but utilises aluminium magnet keepers for more positive magnet security and better cooling air flow. I also did a bit of coil shape optimisation (magnetic field computer simulation). I have a 6 pole (1000RPM) and 4 pole(1500RPM) version. I calculate that these machines will be capable of 4~6kW maximum, partly due to larger magnets and lower coil resistance, but mainly due to better cooling.
My Mark 1 machines had both pelton and turgo turbine options. I used an Eco-innovation plastic pelton wheel for the high head sites, and two sizes of turgo turbine for lower head sites. I bought the buckets from [email protected] in Italy. My Mark 2 machines will also use three different turbine diameters to accommodate different head sites, but they will be turgo turbines only. I am thinking to make my own turgo buckets, possibly by 3D printing…
I went with circular magnets thinking they would give more sinusoidal voltage. Below is the design coil dimensions of my Mark 2, 6-pole generators. The magnets on this machine will be 70mm diameter running at a pitch circle of 88mm. According to the simulation, this gave the best compromise between high magnet flux capture and low copper volume with good sinusoidal waveform. I haven’t actually built one to test yet though.
The machines are regulated with an electronic load controller (dump load controller). The ELC I am using regulate frequency (eg 50Hz). Voltage seem fairly stable as long as frequency is well regulated. (I am working on my own ELC actually, due to shortcomings with some commercial ones we have tried)
Hope you get some joy out of seeing the work of a fellow renewable energy enthusiast!
Adriaan Kragten has tested one of his small alternator designs and published results showing it is compatible with a 1.02m diameter rotor for a low power wind turbine.
A new chapter 6, “Generator measurements”, has been added to public report KD 678. A teacher of a technical school has built the 8-pole generator of the VIRYA-1.02 and I have measured this generator on my test rig for a 12 V battery load. The torque level of the generator appeared to be lower than expected but the matching in between rotor and generator is still acceptable. The maximum electrical power for the rated wind speed of 8 m/s is about 24 W.
Hi, I have my own Piggott wind turbine for 2 years, a 180cm 350W. I had some trouble about the way a regulator adapts energy to a battery charger or a injector. So I made my own regulator, which is a real MPPT for wind turbine and costs less than 50€. May be you will be interested, so here is the link :
There are many regulators on the market. However they are mostly adapted for solar panels only, and if the curve of delivered power is similar, the way to regulate is different – to resume solar panels use buck converter, wind turbines use boost converter. Many are not MPPT, the PWM regulators are very less efficient than MPPT, and also specific wind turbine MPPT regulators are very expensive.
So, It can be a very good project to self-build our own regulator, after having been built our own Piggott wind Turbine
Adriaan writes: “I have added a new chapter 6 to report KD 645 in which a 10-pole PM-generator is described using the housing and shaft of an asynchronous motor frame size 80. This generator has a stator with no iron in the coils. The tittle of this new chapter is: “Alternative winding with 15 coils”. The original winding is a 1-layer winding with six coils which are laid in twelve outside grooves milled in the Delrin stator bush. The alternative winding has fifteen coils which are laid in thirty, 8 mm holes which are drilled in the Delrin stator bush but this requires a totally different way to lay the winding. De Delrin bush is much stiffer for holes than for grooves so it can be pressed in the aluminium motor housing. I think that more copper can be laid in 30 holes than in 12 grooves and so the winding is more effective. I picture of the original winding is given in figure 1 of KD 645. A picture of the alternative winding is given in figure 3 of KD 645.
Adriaan would be delighted to hear from anyone who wishes to build prototypes. He has a lifetime of experience in the field of small wind turbine design but lacks facilities to do this practical testing at present.
Being off the grid I don’t need to worry so much about “payback” since I do not pay for mains electricity in the first place and the payback to me is immensely more than cutting my running costs. But I was reading the blog of Bill in Monmouthshire who has been running a PowerSpout for six years and has a lot of useful insights to share.
Bill points out that “there is a benefit unique to very small hydros operating 24/7. Putting out power at the relatively low level of 500 watts (+/- 300), the turbine’s output closely matches the base load demand of a property. Base load is made up of that multitude of appliances which are ‘on’ all the time – from battery re-chargers to fridges, freezers, central heating pumps, computers and so on. Totted up their power requirement can typically be 400 watts. That translates over a day to an energy consumption of 10 kWh.”
Whereas solar PV generates great lumps of energy in the middle of the day when people are out at work (so the house demand is low), hydro carries the load 24/7, and meets your needs directly. Solar energy will mostly be exported to the grid (exceeding the demand) but hydro power is mostly available to use (without buying a battery).
Actually the same logic applies to off-grid sites in fact. You probably want a battery to maximise your usage of the resource and allow you to run a normal home off a hydro that only produces half a kilowatt of power. But the battery can be much smaller than I need, with my wind and solar systems. I wish I could have a hydro but there is no suitable site near my house.