Her actual use was about 3 mwh, yielding a surplus of about 2 mwh over the year. Rock on! Pasadena Water & Power won't actually write a check for the balance, but are carrying it forward indefinitely. Eventually, I suppose, they will figure out a way for her to cash in. I figure that someday she will be able to buy an electric car, and the extra production (plus the surplus stashed away in her utility bill) will go toward charging it.
Before installing the panels, she had whittled her electricity usage from about 32 kwh a day down to about 13. I thought it would be interesting to see the how things look now.
I decided to invert the Y-axis to represent net energy balance from the homeowner's point of view. Negative numbers represent net consumption, positive numbers are net production. The green region indicates the interval since the panels were installed. PWD bills on a bi-monthly basis, so unfortunately there are not very many data points.
The panels were installed in the middle of a billing period, so the first data point lifts away from the prior trend, and settles on a new trend. The third point in the green region -- the one that dips back into the negative -- is the middle of winter. Production was lowest, and my mom was running a space heater at her desk to keep her feet warm.
But that's just my personal preference. Others may feel differently. However, there is another very simple economic reason why tax breaks are a stupid way of encouraging businesses, especially new industries. As Todd Woody writes, if you give a generous tax break to a small company, it often doesn't have the income to take advantage of the incentive. So, it has to form a tax equity partnership with another company that can use the tax break. With the credit markets screwed up, and Wall Street burning equity like books at Bebelplatz, it's gotten pretty damn hard to put together tax equity partnerships. Not to mention that if you are big company taking large losses, your writeoffs probably provide all the tax relief you need.
Under good conditions, the senior partner in the tax equity partnership often stands to gain a lot more than the junior partner, and the incentives end up helping the wrong people. Under current conditions, few companies are lucky enough to actually need a tax equity partnership with a scrappy little solar company with big plans. End result: a lot of those tax breaks are worthless to the people they are intended to help. Worse still, the more urgently the help is needed (like when the economy stinks), the more useless the tax breaks become.
So, enough with the tax breaks. They are stupid. If the government wants to help establish a new industry, as it did with semiconductors, the internet, and electricity, there are much more sensible options. For example :
- Invest directly, especially in R&D.
- Establish public trust funds to take equity positions in promising companies.
- Agree to buy the product at a predictable price.
The array produces between one and three kilowatt-hours for every hour of sunlight, so for today's half-day of production, we've generated 13 kwh.
Here's the read-out on the inverter :
Sadly, I don't have a way of getting the data out of the inverter yet. Once I add the RS-232 module, I'll have have more interesting things to say about our system. I'll post some pictures of the array itself once we've passed inspection.
The Sunny Boy inverter has an interesting user interface. There aren't any buttons -- you interact with the display by knocking on the front panel with your knuckle.
- 14 SunPower 230 watt panels
- One SMA Sunny Boy 3000 inverter
- A second digital utility meter
- AC and DC disconnects with lockout-tagout switches.
Here is the equipment after delivery and upacking :
We were supposed to get a Sunny Beam monitoring station, but evidently there are some issues with buggy firmware, so they won't be available until September (more about that later).
So far, roof has been preped, the mounting rails are installed, the conduits are bolted in place, the DC wires are pulled, and the inverter has been bolted down. All that's left is to hang the panels, do the AC wiring, and get the inspection.
The installer crew was supposed to finish that on Friday, but evidently they decided to take the day off. The project manager at EE Solar pitched a fit. Nick, the crew boss, called on Friday to say he was really sorry. I told him that his schedule is his business, but if he can't come when he promised, he ought to let us know. On Moday, I'll ask him to run some extra conduit for ethernet to make amends.
So, if you live in the city, then you really need to listen to your doctor if she tells you to lower your LDL/HDL levels.
Anyway, I suppose PG&E is moving in the right direction by building the world's largest solar plant in Southern California -- a 6000 acre, half-gigawatt solar thermal plant in the Mojave desert. PG&E has contracted Solel, and Israeli company specializing in solar energy, to build the plant. There are already nine solar thermal plants operating in the Mojave desert, totaling 354 megawatts in capacity. When the new plant comes online, Mojave will have nearly a gigawatt of solar thermal generating capacity.
According to LADWP, the city's peak demand is 5.7 gigawatts, and a little more than half of that demand, or about 2.97 gigawatts, is met by burning coal. Assuming LADWP substitutes the new solar thermal capacity for coal capacity, LADWP could reduce its utilization of coal generating capacity, and thus emissions from coal, by about 18%. That's a significant chunk, but not nearly good enough.