Merging Wind, PV & Batteries for RE & Independence: Page 3 of 3

Intermediate

Inside this Article

William Bassett with the hybrid system that makes his 19th century farmstead energy independent.
A Weaver 5 wind turbine with 210 square feet of swept area and 11.4 kW of SolarWorld PV modules provide more than 100% of the grid-tied home’s year-round energy use.
An insulated battery box houses 120 Elite Power Solutions GBS-LFMP40AH, lithium-iron-phosphate battery cells. Provides 40 Ah at 384 VDC.
LiFeMnPO4 batteries require a battery management system (BMS) for each 3.2 V cell.
At the base of the tower are the short-circuit brake switch (left) and tail motor disconnect (right), both fitted with lightning arrestors. The box below the tail motor switch houses connection to additional wired anemometers on the tower.
With bidirectional DC and AC ports, the multimode DRI-10 inverter handles either PV or wind DC input and provides MPPT charge control for PV. It can be used with high-voltage battery banks, and can be connected to the utility grid, an AC generator, or neither.
The DRI-10 inverter’s touch screen displaying that there’s 7.3 kW of PV power on the PV port and 5.0 kW of wind power coming in via the load port—the arrows indicate direction of current flow.
William with his Nissan Leaf electric car, which is powered entirely by the sun and wind.

Energy use for the Leaf is typically 3.5 to 4.0 miles per kWh. So if I drive 12,000 miles annually, that means it consumes 3,000 to 3,429 kWh each year, which is about equal to the wind generator’s output. As such, the PV system’s output—estimated to be about 14,000 kWh annually—covers all other household loads, about 20 kWh/day or 7,300 kWh per year. This leaves some surplus energy (about 6,700 kWh per year) that we could use, perhaps for electric space heating to displace some of the fuel we’re currently burning.

We’ve never done a load analysis in our home, but by adding solar, we’re producing more than our usage—even with charging the EV. Should the grid go down, I probably won’t charge the Leaf until I verify that I have ample energy from the PV and wind systems. I have driven the Leaf 3,491 miles in the 17 months since I bought it, and all of those were within 15 miles of the center of Ithaca. So my driving habits fit very nicely with the Leaf’s specs.

Cost & Motivation

The cost—$127,000—for the wind, PV array, and battery systems seemed reasonable considering the system’s novelty and complexity. The 30% federal tax credit applied to both the wind and PV systems. And a New York State Energy Research and Development Authority (NYSERDA) wind incentive of $11,525 reduced the upfront cost of the wind system. (There is also an NYSERDA incentive for PV systems. However, there were going to be delays in getting the DRI-10 approved for the NYSERDA incentive, so we sacrificed receiving this incentive to expedite the project.)

I’ve been asked how long the payback is, and what effect it has on my monthly bills. I don’t know, because saving money was not my main motive, although I certainly have no objections to it.

web extras
“Adding Battery Backup to Your PV System with AC-Coupling” by Justine Sanchez • homepower.com/168.38

Comments (3)

bonneygaj@6508's picture

you are doing excellent.,i am living in guyana nn south america,i have been in wind and solar since 1975,from using air 403 wind turbines,for our micro systems.we have moved up to 1.5 kw grid tie with battery back up ....i am at present paying one tenth of what i used to pay.no ac,for my home is located 100 yds from the atlantic ocean..this is a tropical country,...i even dont have need for fans, for i designed hy home to keep cool naturally...most nights i have to use a blanket, for it can be too cold,i am proud to not depend completely on fossil fuel!!

Robert Pollock_2's picture

Very nice and timely. We're planning a Net Zero house in Ontario, only a few miles North of where you are, with less snow, actually.
My own design/calculations using SketchUp and energy analysis software was pointing at a similar system. You pointed out a few fairly sophisticated approaches however, being in 'smooth air' for one, and the business about DC Voltage. Thanks a lot.
We'll be putting the solar array on the ground with a single axis tracker, depending on what a dual axis costs and how much trouble it might be. Also a Passive Institute design, not that I copied them, we just ended up at the same place, and a ground source heat pump. (mini-split) Burning wood intrigues me. I think you can burn it fairly cleanly by letting the stove run wide open and mitigating the excess heat with a masonry thermal mass surround, maybe ten tons. When you live in the woods it seems so silly to not be able to burn wood. Really dry and burned at 1400 F or so, what gases and particulates are emitted and how much?

ideas2014's picture

is it possible to share the single line wirring diagram with us , if i send u my email
thanx

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