Made in Japan (part 3)

Back in November 2008, while out sightseeing at the dammed lake reservoir near Miharu, we stopped at a hotel spa place that has a very good tofu cafe that sells all sorts of yummy food entirely (almost) made from tofu or derivatives (even the donuts!).

Anyway, while walking about I noticed that somehow they had also built an observatory (it gets very dark up here in the mountains away from any town).  

Next to the observatory was what at first glance appeared to be a bus shelter (err.. because it had buses parked under it).  In fact it was a sizeable solar array!

It consists of 8 rows of 14 x 167W 48 cell (23.2V MPP) Kyocera panels (I could read the info plates on the undersides).  From the date stamps on the panels it seems to have been in operation since 2002.  The nominal output is 18.7kW - maybe enough to offset most of the power used by the small hotel, observatory and cafe.

The electronics were all in a sort of phone box shaped hut next to the back row.

Travelling from the remote town of Takayama through the mountains to Matsumoto I saw quite a few new looking home based PV systems but many more old looking solar hot water systems.  These types of evacuated tube or flat plate collectors have been popular for decades with the Japanese.

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.

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.