One year ago, we connected our solar inverter to the grid. It had been repaired under warranty for noise, it is still not within specification, far from it, but for power the system does perform. If all years are as good as this first year, when we sold 2757kWh and consumed the rest we will reach payback break-even in 11 years, not in 13 years as we initially expected.
So, how was life with solar?
Yokohama Green Power
Solar electricity works only a few hours a day, but with subsidies through the YGP program we could take advantage of a favorable price for installation and feed-in tariff. Up to a degree solar helps ease the peak daytime load in summer and if there is decent storage (there isn't, yet) it may provide great emergency backup power. During the power outage of the 2011-03-11 desaster, we could charge our phones with the waning daylight, but overnight, no sun, no solar electricity.
Utilities in Japan had effectivelly stalled alternative energies with regulatory red tape, which killed quite a few companies that may have had great technology. Some that were wise enough to build up a customer base abroad survived. For example, combined heat and power generation can easily save 30-40% CO2 and cost for the same residential energy use, but up to now (the diet is planning to change that) a small home use cogeneration plant is not allowed to feed back any such green electricity, it has to be wasted in resistive heating.
Yet, we calculate such a micro CHP unit would return its investment in about 14 years, a fuel cell in 17 years, while a gas boiler replacement due every 10-15 years would be just sunk cost. And in Japan, condensation-type boilers that use the gas energy some 10% more efficiently have only been available since last year, almost 20 years after Germany. The nuclear disaster and energy crunch has added necessity on many levels to look for better technology.
Why no data? It is ours!
Part of the Yokohama Green Power subsidy went to cover the cost of a HEMS, a Home Energy Monitoring System that shares our generation and consumption data with the Yokohama City's YGP project. Well, the Toshiba feminity system (its real name) turns out quite the lemon.
We can read near-realtime data, like every 30 seconds or so, but does that help us reduce energy consumption? Not a bit. We would have to run a computer to see the display, dispalcing a lot of potential saving from the outset. The monthly statistics graph is entirely unusable. This system does not even give us a table of our own generation and consumption data. We had to request it from Toshiba/ YGP and hope we get that soon.
Solar system owners in Germany share generation data on the web, with the added benefit that the maintenance company get an alert if they compare power generation with neighbors and detect the need for maintenance in case the solar harvest falls against other systems nearby with essentially the same weather pattern.
HEMS is not worth it
To have a full HEMS Home Energy Management System, we would have to replace all our 36 switches, which easily adds 1200kWh standby per year, costing some 27,000 yen on the annual electricity bill with no way to recover that from reduced energy usage. In my view, digital home control is a nice toy, but not relevant for saving energy, unless you have large energy storage units, which anyway come with their own digital controls. So much for smart grid at home: no need, no benefit. Even assuming new technology reduces the standby power significantly, there is still the risk of component defect, data leakage, and misuse. Better stay with the simple old switches and replace some incandescent bulbs with LED lights for a payback within 4 years. Was surprised the other day, this video had gotten more than 30,000 views and I have no idea why.
Would we do it again?
This question amounts to asking, "among technologies within our reach, which would we first install for economic and ecological benefits?" The simple answer: earliest payback first, that is usually energy-saving measures, such as 4 years for LED lights replacing incandescent. Or properly adjusting the gas boilers with a CO-meter. Some of ours consumed way more energy than necessary because of too much air flow.
Here is our solar payback calculation, based on subsidized installation cost and feed-in tariff of 48 yen / kWh (guaranteed for 10 years) with daytime electricity cost of 28 yen / kWh (night 8 plan). Rising utility rates would reduce time to payback.
Click image to see large.
With most low-hanging savings fruit in the basket, we go for technology that reduces our eco-footprint and still has reasonable reliability and payback, such as cogeneration gas engine (14 years) or cogeneration fuel cell (17 years with subsidy).
Nice, but this is not the breakthrough technology this society needs now. Anything else you could put within our reach?