Our household of four uses about 500 kWh of electricity per month on average, a considerable portion of which is consumed by the computers I run my business on. The total tends to be more in July and August, when we also run air conditioners to take the edge of 35+ centigrade heat, whereas in the winter our municipal gas bill tends to go up a lot because of heating. All year round we use gas for cooking and hot water.
TEPCO (Tokyo Electric Power Company), the local utility for the Kanto area, charges us about 25 yen per kWh on average (the exact rate varies a bit month by month, as the company tries to even out charges for its customers against seasonal consumption patterns). That’s about US$0.28 / EUR 0.18 per kWh at current exchange rates.
While electricity in Japan tends to be expensive by US standards, its supply is also extremely reliable. Until a few years ago uninterruptable power supplies (UPS) for domestic use used to be almost unheard of here, because we’d expect maybe one brief blackout per year. The Japanese power grid tends to be a lot more redundantly laid out and with more spare capacity than in the US, where cost is the top priority.
The voltage of A/C power in Japan is 100 V compared to 230 V in Europe and 110V in the US. Western Japan (Nagoya, Osaka and further west) uses a mains frequency of 60 Hz like the US whereas Eastern Japan (including Tokyo) uses 50 Hz like Europe. Equipment sold in Japan works with either frequency, but often the Wattage rating is slightly different depending on the frequency. Japan uses two pin plugs like ungrounded US plugs and usually they’re not polarized. If equipment has a ground wire it is attached separately, not via a plug pin.
Electrical appliances purchased in the US will usually work OK at the slightly lower voltage of Japan, but the reverse is more risky. I once managed to fry a power brick for a USB hard disk which I took to the US and used without a step-down transformer (110 V to 100 V). Moving between Europe and Japan, a transformer is almost always required, with the exception of consumer electronics items that use a 100-240 V universal switched mode power supply. These days the latter category includes almost all notebook computers, digital cameras, video cameras and many desktop computers, flat screen monitors, etc.
Japan generates about 30% of its electricity from nuclear power, 7% from hydroelectric dams and the rest from fossil fuels including coal, natural gas (imported as LNG) and oil.
In recent years the electric utility companies have been aggressively promoting “orudenka” (all electric power) homes, i.e. new homes that use electricity for cooking, cooling, heating and hot water, with no propane, natural gas or heating oil usage in the house.
So called “EcoCute” heat pumps produce hot water using ambient heat and electricity. Even if they manage to provide two extra units of heat for every unit of electricity, they are unlikely to save much CO2 output compared to burning gas, as fossil fueled power plants only produce one unit of electricity for every three units of heat from burning fuel. Yes, it may be better to use a heat pump to make hot water from electricity than a simple heater element, but at the power station you’re still wasting 60-70 percent of the primary energy from coal, oil or LNG, which goes as waste heat into a river or ocean or up a cooling tower. It would make more sense to burn gas at home to heat water, instead of two conversions (from heat to electricity to heat) and transmission losses. With the current power infrastructure EcoCute is hardly the way of the future.
EcoCute would make sense only with plenty of wind, geothermal or hydro power to supply electricity without pumping out CO2 or piling up toxic radioactive waste. In reality Japan is generating almost two thirds of its power from fossil fuels. Its utility companies are sitting on piles of nuclear waste that has nowhere to go. Japan is lagging far behind other developed countries in wind power or other renewable energy sources while confidence in its nuclear industry has been shaken by several high profile accidents since the 1990s.
If you’re going to burn anything at all to make electricity (as we’ll probably have to for a few more decades), a much more promising concept is the “Ene Farm” combined heat and power (CHP) generator promoted by several gas utilities and oil companies, launched in Japan in June 2009. It’s a residential fuel cell producing electricity from hydrogen and oxygen while heating water with the waste heat. Like in prototype automative fuel cells (e.g. Honda), the hydrogen is extracted from natural gas through a process called steam reformation. A fuel cell CHP system located where heat can be used directly is about the most economical way imaginable of using fossil fuel, if you’re going to use it at all.
The biggest current drawback of Ene Farm is the high cost of the system: 3,255,000 yen ($US36,000) for a system that puts out 250 to 700 W of power and a multiple of that in heat that goes into a 200 l storage tank. A 1,400,000 yen subsidy by government does make it a bit more affordable, but still its cost needs to come way down to make it popular enough to make a big dent in CO2 emissions from Japanese homes. Its proponents are hoping to reduce the equipment cost by as much as 90% over the next decade. I hope they succeed – at a lower price it could be a killer product.
A very similar idea, but taking a different route is the Linear Free Piston Stirling Engine (LFPSE) cogeneration unit jointly developed by Infinia, Enatec, Bosch and Rinnai (a Japanese maker of gas appliances). Instead of a fuel cell it uses a Stirling engine to convert heat into mechanical motion, which via a moving coil generates electricity. The waste heat produces hot water or heats a home. First generation prototypes are being tested in Europe from 2008 to 2010, with mass production by Rinnai in Japan scheduled for 2011.
Why not go with the all electric home that has an integrated photoelectric system? The photoelectricity could power the the heat pump to provide hot water and air conditioning without the pollution you were worried about.
Residential photoelectricity costs in Japan will head down sharply in 2010 due to subsidy cuts in Germany. Japan could well gain the number one spot back from Germany in 2010 or 2011. Keep an eye out.
since last year power from photovoltaic panels can be fed back into the Japanese grid and the utility company will pay a feed-in rate of 48 yen per kWh, roughly twice as much as we pay for power we draw from the grid. In other words, if households produce as little as one third of their electricity usage from solar panels, they end up paying nothing at all!
While this helps to compensate for the high cost of installing these systems, the flip side is that every extra kWh that you use will effectively cost you 48 yen ($0.53 at current exchange rates). From an economic point you’re better off aiming to reduce your electricity consumption as much as possible, even when you make your own power, if you can sell the power at a subsidized rate. This is why combining photovoltaic panels with “orudenka” (all electric appliance) households doesn’t really make that much sense.
Even ignoring the subsidized feed-in tariff, using solar panels that are maybe 10% efficient that then produce maybe twice the thermal output via a heat pump probably can’t compete against thermal solar collectors that directly make warm water on your roof. They would be far more cost effective for this purpose. Ideally, photovoltaic cells would be combined with a water cooling system that keeps them operating at peak efficiency (output voltage drops with rising temperatures due to higher internal resistance) while producing warm water for domestic use.
A concave light reflecting mirror focusing on water pipe to make hot water and feed the excess hot water to a stirling engine attach to generator would be a nice project, wouldn’t it?
Since, Photovoltaic panels are not that efficient. They are great for smaller scales like portable USB charger though 😛
Concave mirrors work well in sunny, dry climates, but no so well everywhere else. Photovoltaic cells by contrast still produce decent amounts of power when solar radiation is a bit more scattered.
To run a Stirling engine efficiently you want as much temperature difference as possible between the hot and cold side, so you would probably heat the stirling engine from the mirror and produce warm water from the waste heat of the engine, not the other way round as you suggest.
Japan has a humid climate with frequent cloud coverage, a stirling engine with mirrors would work nowhere near as well as in New Mexico, Arizona, Southern California etc. On the other hand wind power would work well in Japan.
A lot of solar USB chargers are little more than glorified spare batteries, as their internal storage batteries would take much longer to recharge from solar energy than from a USB cable / AC adapter. The tiny solar panels on them are more of a clever marketing gimmick than a practical solution. They are also relatively expensive compared to larger panels where you get economies of scale.
What I meant on the Stirling engine was to have a hybrid system one stores the heated water directly to an insulated tank, if the tank is full use the heat water to heat the heat exchanger on a Stirling engine. Japan is cold and windy so I don’t know whether the system could capture enough heat for the Stirling engine or not.
Of course, Wind power is much more efficient on the condition that you can get constant wind since we can directly covert mechanical power to electric. Whereas, Stirling engine have to convert heat>mechanical>electricity.
To fully charge a Li battery more power is required as approaches it’s maximum capacity. Providing there is a constant light for PV to charge the device it might be slightly better than spare batteries.
But then again PV is much more fragile and if you couldn’t get enough light then it’s useless. imho.
A Stirling engine running on at most 100C water would not really be very efficient. Ideally there should be hundreds of degrees of difference in temperature between the hot and cold side.
You can’t say that Japan is a cold country, at least not the parts where most of its population lives: Tokyo lies closer to the equator than the southern tip of Spain. It does have a long coast line that makes it suitable for wind power (on shore or offshore), as well as a lot of mountains in its interior.
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