First day of solar production
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.
Russell:
I am interested in your solar system and what made you install a large (3kW) system.
I have recently installed a 1kW system (May 20) using a Sunny Boy 1700 and Sunny Beam monitor.
It is winter here in Melbourne Australia, so we only get about 8 hours of daylight. In the past month I have only generated about 50 kWh. On sunny days it makes 3 kWh and on overcast days it can be as low as 0.3 kWh. I have allowed for another 700 watts of solar panels to be added in future.
Economics
The system cost A$13,000 (A$1=US$0.95) but the government gives us a A$8,000 rebate so the net cost is around A$5000. We also have a feed-in tariff of $0.60/kWh for all energy fed back to the grid.
The dual tariff meter measures total power from grid, but also accumulates power fed back to grid.
On a sunny winter’s day the system feeds about 1 kWh per day back to the grid but takes 8 kWh from the grid.
We pay $0.17 per kWh for grid power so cost per day of power is about $0.75. Without the solar system the cost would be $1.87 per day or a saving of up to $1/day. I estimate the year round saving will average out at about $1.50/day or $550 per year. The pay back period will be around 8 years or about 11% PA. Without government grants and feed-in tariffs the payback would be about 30 years or 3% PA making it completely uneconomic.
I would be interested to see you economics.
Sunny Beam
I was interested in your comments regarding Sunny Beam not being available as I have not found any firmware problems with my system. The main problem is the hopeless range it has because the aerial is located on the underside of the Sunny Boy. As I have a two storey house the upper floor is in a radio shadow so the Sunny Beam has to be within about 15 feet of the Sunny Boy for the Sunny Beam to receive any signal.
Peter Kay
Melbourne Australia
Peter --
Thanks for asking! I'm always glad to hear from other people who've actually gone through this process.
The economics here are a little different. We get a bigger subsidy ($2000 from the Federal government and $8000 from the local utility), but we don't get a feed-in tarrif. The law just says that the power company has to buy power from us at the same price it sells it.
The federal and utility subsidies are awarded based on a roughly linear scale, with a maximum and minimum. The installation cost per watt declines as the system size increases. There are a lot of fixed costs for this kind of system; conduits, wiring, rails, roofing material, pylons, saftey hardware, inverter, and labor. Those aren't really fixed costs, of course, because a larger system will require a few more pylons, a few more wires, rails et cetera. But they don't scale linearly with the system size.
Our objective was to minimize the dollars per watt. Given the way the costs and the subsidies scale, the "sweet spot" happens when you just barely qualify for the maximum subsidy. We have perfect orientation, no shading, and an average of 7 hours of sunlight per day, so the sweet spot is right around 3 kilowatts.
Because we don't have feed-in tarrifs in the US, it's impossible to say for sure what the time-to-payoff is. Right now, we are paying $0.15 per kwh, and it seems that the utility raises the rates by about $0.02 per year. California has a pretty unstable energy market, so it's hard to guess where things are going. We are making a bet that the rate increases will continue, and probably accelerate.
We produce about 21 kwh a day, and we use between 9 and 17. In the winter time, I expect that we'll underproduce, but the system is less than a month old, so I'm just making a guess based on the USGS data. I designed the system so that we should be net-zero over a year.
I'll be posting more about our system once I have serial access to the inverter. I also have some financial projections that might be interesting, but I need to calibrate them with a year's worth of data.
It sounds like we used some pretty different assumptions when we designed our systems. Can you describe the planning process you went through? Do you have any photos?
True
Russell:
The planning process was simple as the $8000 government grant cuts out at 1kW peak power. The high feed-in tariff cuts out at 2kW installed capacity.
I sized the inverter to allow another 700W of panels to be added later if they get cheaper. At the moment the panels cost about $10 per watt.
I also have a 500W wind generator that I bought on eBay for about $800 but so far it has been a flop. The maximum I have seen it generate is about 150W mainly because I have it installed too close to a eucalypt tree which shades it from the prevailing wind. I will try relocating it next spring to see if I can get better output. It currently is charging batteries and I have a 24VDC to 240VAC inverter connected to it. If I can get more reliable power out of it, I could probably rectify the 240V and feed in 240VDC into the Sunny Boy or even a Windy Boy if that does not work.
I have photos but cannot post them here. What is your email address? Mine is kay.peter@gmail.com.
Peter
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