Monday, May 31, 2010

Made in Japan (part 2)

This time we're in Miharu in the prefecture of Fukushima to the NNE of Tokyo by some 200km.

If you keep hitting (+) on the map it will zoom in and show Miharu (eventually!).

My father-in-law's house has two arrays on the South and West facing roof slopes and luckily even though it is in a quite steep valley, the valley runs East to West and his house is on the North side so it gets a fair bit of sun even in the winter.

The panels are made by Hitachi and are their newest hybrid crystalline amorphous type that have layers that give excellent wide spectrum responsiveness on cloudy days but the high output of crystalline panels on sunny days. The Sharp ones used on the house in Tokyo were a common crystalline type. On the South roof there are 18 panels and another 13 on the West roof.
All the power conversion kit is made by Sanyo.

As the array is split into unequal strings of 18 and 13 panels, they work at two different DC voltages. So outside on the wall is a voltage converter / combiner that converts the two different DC supplies into one at a common voltage that then goes into the inverter indoors.
A single DC cable goes to the power conditioner in the house where it is converted to mains. It's a less elaborate unit than the Sharp one and just has a single display that toggles between current kW output and the lifetime kWh generated. The information plate says it is rated for 70-380V DC input and 5.5kW output at 200VAC with an efficiency of 95%.
Outside, the utility company has fitted two digital electric meters, again one for power used and another for surplus power sold to the grid.
The inverter appears to be putting out 200V rather than the house 100V, so either it's designed to be split phase (100-0-100) relative to earth or it actually doesn't feed the house directly but just the grid through the separate meter so that the household usage bill is offset by the generating credits.

My father-in-law said that in the summer and up until September it generates a net surplus to the household requirements but by November it doesn't quite make enough to completely offset their usage.  On the clear sunny day shown here, the inverter reported making 3.0kW for a short while around mid-day but 2.1 to 2.6kW for the bulk of the day. The sun was quite low in the sky even at noon and as it moved round to the West, the output declined a bit.  In summer it was probably ok with the sun much higher in the sky and on cloudy days it probably doesn't make much difference either having part of the array facing west.

Another novel feature of their house is a Sanyo air source heat pump (ASHP) that heats water by extracting heat from the outside air (usually hot and humid). Using a sort of reverse air conditioner it pumps the heat into an insulated hot water tank. 

It uses about 60-70% less electricity than a resistive heater. The Japanese call it an Eco-Cute. It doesn't mean "cute" though... "kyu" is a kanji in Japanese than means "to heat water". The difference between an ordinary air conditioner compressor and these water heaters is that the refrigerant is at a much higher pressure in this system to more efficiently extract heat and it's only in recent years that they've been made small enough and cheaply enough for home use.

Inside the house is the large hot water tank and compressor. A digital display shows the water temperature and how "full" the hot tank is as a bar graph.
The system also controls the heating of the bath to a constant temperature - very important for Japanese.  You take a shower and wash and then sit in the tub just to relax and get warm while the system cycles the water.  You could sit in it all evening.

He also had the kitchen refitted and they changed from a gas hob for cooking to electric induction.  This wastes a lot less energy (95% of the energy goes into heating the pan rather than the hob or the air) but did have the drawback that they had to replace most of their cookware.  Induction hobs only work on ferrous metal pans, so the typical aluminium or stainless steel with copper bottoms don't work well.  As they generate quite a large surplus of electricity, it made sense to change from gas to electric for cooking.

Saturday, May 29, 2010

Made in Japan (part 1)

It's not just me in my family that has solar power, no sireee.  It was actually my in-laws that started things off.

My wife is Japanese and her sister lives in the suburbs of Tokyo.  Back in 2008 they installed a grid tied 3.07kWp Sun Vista system by Sharp.  

Sharp call the inverter a "power conditioner" and it has a control and info panel near the utility breaker panel indoors.  It lights up different colours during the day to indicate the power level.  Blue means the system is generating a surplus and is selling electricity to the grid and yellow means it is generating but grid power is being used as well.

The panels are mounted on both sides of the roof but the slopes face sort of east and west so one half of the array is always sub-optimal. The sun doesn't make such a low angle in winter in Tokyo when compared to the south of the UK so the variation of day hours are less extreme and Japanese Autumns and Winters are characterised by clear sunny days (very unlike the UK). In the summer the sun goes mostly directly overhead so it's not such a problem.

Their house is the one at the back of the white one - you can just see the panels on the roof.  The houses are terraced back to back.

The installers mounted the inverter on the outside wall and then ran a wire to the remote control panel inside.
The mains is fed to two meters outside that the utility company installed.  The digital one on the left measures grid power drawn and the old school mechanical one on the right measures solar power sold to the grid.

The remote panel in the house displays an estimate of power being generated as well as the proportion being used or sold and the lifetime kWh. Flicking through the menus you can pull up generating history graphs for the last hour, day, week, or month.

It's about 11am in this shot and it's just started to make a surplus now that we are done with breakfast and have stopped using the kettle.  The sun is a bit hazy today. 

They tend to sell a lot of power during the weekdays when they are out at work but then buy it back at the weekends when they use the air conditioning and clothes dryer.

The whole system is a kit made by Sharp but a local installation company fitted it.

Wednesday, May 26, 2010

PV in Germany

I knew that solar was more popular in Germany than the UK but this set of pictures gives you some idea just how far ahead they are compared to us in the UK...

I wasn't intending to go on holiday in Germany but fate (or rather volcanic ash) interceded and we had our flights to Japan cancelled.  So, not wanting to spend the whole of the four weeks I'd booked off sitting in our back yard, we caught the ferry to France and drove across to Germany.  We went to Seiffen near the Czech border and up to Berlin and across to the Nurburgring (but I couldn't drive on it as my insurance excludes it by name!).

Along the way, we were amazed by how many houses had solar PV or thermal (sometimes both) and here is a sample of what we saw.  The biggest array by far was one in the "back yard" of Amazon's warehouse in the middle of nowhere in the middle of Germany.  Absolutely huge it was.... a whole field of trackers.

Some like this one are communal, shared somehow by the residents of a block of flats.  This one has 121 panels and at a typical 180Wp per panel that's about 21.7kWp

Many businesses install very big arrays on their warehouses or factories.

This was one pair we saw from the window of our castle hotel at Neuhausen near Seiffen that specialises in wooden toys and other intricate wooden decorations.  You can see the 88 panel array on the house but also a bigger one on the barn just peeking over the hills behind.  This house had in the region of 15.8kWp installed.  And this is quite common in Germany.
These two we saw in another castle town, Wernigerode, where we stayed at a ski hotel.  This house must get through a lot of hot water! It has a massive thermal solar panel.
This one not only has panels all over the roof but also on angles all over two garages / sheds to the left of the house.
Driving in the scenic valleys to the North of Kassel, we saw a solar showroom.  A big ex-supermarket type building with a large car park.  Could solar be so popular that they have something akin to a car showroom for selling installations?  A helpful woman enquired if I needed help.  I looked at a selection of example panels they had in different powers and styles (including black framed ones and big amorphous ones).  They stocked some brands but she pointed out that they also made their own brand too.

Driving on through that town we started to see more and more installed PV systems... Obviously, the showroom had been doing plenty of deals for the 'Burghers.

Driving along the 80 towards the fairytale town of Hameln (as in the Pied Piper of), we were stopped in our tracks by the sight of this village (Oedelsheim) with its numerous houses with big PV arrays.
The farmhouse on the far left having some 264 modules installed on the upper and lower roof! I did notice on my travels that mostly the Germans seem to go for poly panels rather than mono types.  Maybe they're a lot cheaper or perhaps the German made ones are predominantly poly types?
The neighbours were keen to keep up with the Johans in some arms race to see who could have the biggest array.
Hameln Banhof (train station) has this bus station with see-though panels specially made to make power and act as a sun shade. They are not so different to normal panels just the cells are spaced out a bit and a clear backing used instead of the usual white / blue EVA.

Treysa in Schwalmstadt to the SE of Kassel has a walled old town and from the ruin of the church you can see this school complex with a massive PV array on several buildings.
This office, visible from the old town wall has 198 panels (~35.6kWp) installed.  By now this looks "average" as installations go.
Even some of the old timbered houses in the town have been kitted out.  Not sure massive solar arrays on quaint English Tudor houses would sit well with the parish council but the Germans don't seem to mind.
Just outside the nearby castle village of Ziegenhain (supposedly the town of Red Riding Hood) some nutter has put a 5x5 module tracker on his shed...
Ferienhof Todenhausen wins the award for the most solar systems installed in one village though...  It's not that big a place but it has a crazy amount of PV installed.
I counted 14 PV / thermal installations on different houses in this close-up shot alone.
And someone went mad on the far right of this shot where they installed PV all over the two enormous grey sheds with specially designed sloping roofs!
All the excitement went to me head and I bought the used 50W panel and 5x new 80W panels off of eBay for me home brew setup when we came back home.

On the way to Yorkshire to pick up the 80W panels, I noticed plenty of large buildings (offices, warehouses, farm buildings, homes) that were all ideal candidates for massive PV arrays that would almost certainly had one if they were in Germany... Not a sausage here.  Pitiful.

Tuesday, May 25, 2010

Last of the New BP Panels

The weather was hot, the sun blazed but I persevered.

When I bought the last five panels, I'd only thought about using four of them as I have to use pairs of panels to make 35V strings for charging 24V batteries.  I had thought that I might sell the spare one or wait until I found another to go with it.

But then it dawned on me that I already had 2x 40W Kyocera panels on the garage roof.  By connecting these in parallel to make an 80W "panel" and then the spare 80W panel in series, I could use the last BP panel and get rid of the last of the plastic 15W panels.

With this, my system increased marginally to 1,798Wp but probably makes much closer to this figure now as the 15W panels only seemed to put out about 80% of their official rating after about 6 months in the sun.  Amorphous panels do degrade as they are first used but makers are supposed to factor this into their rating so that they declare a panel as being 15W after the stabilisation period.  Some unscrupulous makers only declare the "Day One" power output though...

With this lot I've been making up to 63% of all my electricity needs each day (well at least 50% for the last three days in a row).

The main benefit has been free hot water each day with my automated water heater dump load absorbing all the spare solar power at lunchtime.

I'm not sure I'd want my panels on the house roof as they keep getting covered in dust and so I wash them about once a week with a pressure sprayer.  It seems it's not actually just dust but loads of yellow pollen from trees nearby that is settling on them.  Bird poo is also a problem as a large seagull one can cover a whole cell and then stop an entire pair of panels from charging the batteries.

Back in April, I did notice some of that volcanic ash collecting on them too.  Not a lot but you could see some specks of what looked like burnt paper that were so fine they turned into a grey smudge if you touched them.

Saturday, May 22, 2010

More Batteries

The solar gel batteries I have are fine... I haven't managed to kill them (yet).

But they aren't terribly big.  Only 180Ah.  If I watch a couple of movies on the video projector (that electrically resembles a fan heater!) the batteries soon run down to 50% or less.

Another issue was that I've now got so much solar power available that it's actually a bit too much for the gel battery bank to absorb all at once.  On a good day, I've seen charge rates as high as 56 Amps and the makers of the solar batteries recommended that I keep it under 30 Amps...  More batteries to share the charge current and to add some spare capacity to "help out" when the main batteries were under the cosh were the answer.  

I had a load of old tired wet batteries from a couple of years ago and these sort of helped but only when the gel bank was getting quite low.  They also couldn't help much as they had lost a lot of capacity.  I measured them on a load a couple of months ago and when new they were 110Ah but now could only muster about 35Ah to flat...

The other problem with them was that (as usual) when charging, they made gas that is explosive and not very pleasant to sniff.

I decided to try some used uninterruptable power supply (UPS) batteries from a regular seller on eBay.  He gets various types of battery from small 38Ah 12V packs to 1600Ah 2V cells.  Data centres usually replace their UPS batteries on a fixed schedule to avoid taking any risks with them failing when called upon to work in a power cut.  Some of the batteries he gets are from companies that have gone bankrupt.

The only problem is size and weight and collecting them.  Luckily, last Monday I was in Wales for a meeting and on Tuesday on the way home I had to pass within a few miles of his place.  So I decided to try a couple of 105Ah 12V AGM packs.  These were £50 each and only a couple of years old so presumably came from one of the many companies that have gone bust in these times or from one that had to upgrade to a bigger power supply.

They seem to be ok and after a conditioning charge to bring them up to full after having been in a shed for a few months, I connected them up to the gel batteries via a 30A fuse.  They are much more willing to assist the gel bank when loaded and also absorb solar charge much more greedily than the old wet batteries.

Being sealed batteries, they also don't release any gas and can be used on their sides without the acid spilling out as it is held in place by a compressed glass mat "sponge" between the lead plates.  Their flat profile also means that I can turn them on their side and keep them under the sofa :D.

If they work out, I  might buy some more.

Thursday, May 20, 2010

The Story So Far... (part 3)

Having gotten bored of running up the stairs to turn on and off the water heater, I started looking around for a way to do this automatically.

The answer came in the form of a Velleman kit from Maplins called snappily a K8055 USB experiment interface.  It allows a PC to read switches and sensors and then output signals or turn on / off relay switches.  You can get them either pre-made or in kit form and you have to solder it together yourself.  I chose the kit version as it's £10 cheaper.

After putting it all together, it looks something like this...

The inputs are the terminal blocks on the left (two analogue inputs of 0-5V and four inputs for switches).  The kit actually included little press buttons to test it with but I didn't bother installing them.  On the right are the outputs (8 on/off outputs with LEDs and two analogue outputs of either 0-5V or PWM of 0-100%).

The latter could be used to dim a light or even a heater by varying the duty cycle of power to the load and using thyristor to chop the power.

A CD comes with the board that has the Windows DLL that makes it work and an example program in various languages.  I had an old copy of Visual Basic 6 sitting around and it works fine with this.  To make my program to control the heater, I just took the demo program and modified it a bit.

In order to control the heater so that it only used spare solar power and not battery power, I needed to measure several things:

  1. The voltage of the battery bank.
  2. The mode of the charge controllers (whether they are charging or finished).
  3. How much power the system is generating for loads (including the battery bank).
  4. How bright the sunlight is (to estimate how much solar power is available).
Most of this information is available via the Morningstar charge controllers.  They record this information and it can be read as data via their communications port.  The TriStar MPPT-60 additionally has an Ethernet port so it can be networked.  The main computer in the house is upstairs (conveniently near the water heater) but the solar stuff is downstairs on the other side of the house.

I didn't want to run Ethernet cable all over the house so I used a pair of Ethernet over Power plugs.  These just plug into spare power sockets and then carry data over the house wiring.  Very handy.  This then plugs into an old 10Mbit hub as I also have a couple of computers in the living room and an IP CCTV camera outside.

One of the computers is an old Toshiba laptop that I bought at a car boot sale a couple of years ago for £5.  It works and with a new battery bought off the internet, it even runs better than new.  It only has Windows 98 but I managed to find an old Ethernet card for it - would you believe from another pair of laptops I bought at a car boot sale for £5.  Those laptops were a bit broken but work now and the Ethernet card was free.  The Toshiba can't use modern cards as it isn't Cardbus compatible so I had to find an antique card to use in it.

The Toshiba is plugged into the two charge controllers.  The Ethernet of the TriStar and directly into the serial port on the MPPT-15.  The Morningstar data logger software then records the output and battery state from both controllers and saves it in a CSV file on a network file share (on the PC upstairs).

This data file is read by the program I wrote using the K8055 demo software.  I combine the two sets of output figures for charge Amps from the two controllers and then multiply that by the battery voltage to give a figure for total power generated.  The system records these values every 15 seconds so a graph can be drawn (again by the Morningstar logger software) like this:

The load manager program then takes an input from a light sensor to measure how strong the sunlight is.  The power graphs above only tell you how much power was used, not how much was available.

At first I tried using a light dependent resistor to measure the light but it was too sensitive (they are commonly used to measure how dark it is for dusk to dawn lights).

I tried to cut down the light reaching the sensor by putting it inside a sea shell as these are white and nearly opaque so that they cut out most of the light.  I sealed the sensor inside two such shells with waterproof polyfilla.

Unfortunately, after a couple of weeks, the sensor broke and stopped working so I had to come up with another idea...

This time I used an old miniature solar panel from a AA battery charger and put it in a waterproof box.  I connected it to a 100 Ohm resistor as a load so that the USB A/D input would read the voltage produced as a measure of the power produced and so the strength of the sunshine.

Finally, the K8055 program reads the charge state from the charge controllers (MPPT, Absorption, Float, Equalize, or Night) and uses all this information to try and estimate when there is enough solar power available to charge and keep the batteries full while turning on the water heater.

Here you can see all the information about the solar input (sun strength), power produced by both charge controllers combined and the battery status, along with the information that the water heater has been running for a total time of just over two hours today (it was a bit cloudy).

The output of the K8055 interface card drives a miniature 12V mains relay that just fitted inside an extension lead socket so that the heater (via its 230V to 115V transformer) just plugs into the controller.

I installed a digital thermometer on the water tank (cutting though the foam insulation to glue the sensor on the tank itself about 1/3rd the way down from the top).  For every 10 minutes the water heater runs on solar power, it conveniently increases the tank temperature by 1'C.  Some days in May, the heater can run for almost 6 hours, raising the water from 15'C to over 50'C.

Tuesday, May 18, 2010

The Story So Far... (part 2)

Originally, I just wanted to run my work laptop on solar power.  I thought, "How hard can it be to power a 30W load for 8 hours a day, every day?".  Turns out the answer is, "pretty hard".

The problem is that solar power is very variable and unreliable.  Some days you get loads other days you get nearly nothing.  The batteries help but they are fragile beasties and if not kept charged up fully will soon die (like in a matter of days if left completely flat).  So you are always balancing using the stored solar power in the batteries with not using so much that you kill them.

One thing this leads to is any big constant loads like the water heater are very difficult to run.  Even if you've got enough solar panels installed to run it, you will almost never know if you've got enough solar power coming in to run it.  If not, then the batteries start to drain and you risk not having enough power for the night.

The first problem is that water heaters use an enormous rate of power consumption (typically 3kW).  I've only got 1.8kW of solar panels.  The answer was to reduce the power used by the heater.  The easiest way to do this is by reducing the voltage fed to it.  At 230V, the heater will use 3kW of power.  At 110V, it will only use about 650W.  It will of course take much longer to heat a tank of water at this rate but in the summer, you can count on up to 6 hours of solar power on a good day... More than enough to heat a tank of water to 55'C.

I found an old tool transformer at a car boot sale (I love car boot sales - why buy new when you can buy randomly old?).  Conveniently, this does just what I need; converting 230V solar power to 110V.  So now I only need 650W of reliable solar power to run the water heater.

It wasn't as bad as it looks... Honest.  Just flaky paint and some external rust.  The guy let me have it for £15, not bad considering it was a custom wound 4kVA unit - more than man enough to run a water heater continuously without getting hot or catching fire or 'owt :)

With a bit of Hammerite, things were looking a lot more ship-shape (or at least transformer-shape).

And then off it went to its new home in the airing cupboard.

That leaves you with problem number two...  You could turn the water heater on and off by hand while watching the power levels and the window for clouds to appear and spoil your fun.  I did this at first but quickly grew tired of running up the stairs to the airing cupboard.  So what was needed was an automatic way to measure the solar power, the condition of the batteries and then turn the water heater on and off so that you keep the batteries charged up and only use incoming spare solar power to heat the water.  In off-grid living, this is called a dump load controller.  Something that takes all the spare energy and dumps it somewhere useful (water heaters are the usual dump load of choice).

Coming up in Part 3... A whole lot of bodgery involving a kit from Maplins, a doorstop laptop, some retro 90's software development, seashells and polyfilla...