Merging Wind, PV & Batteries for RE & Independence


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.

In 1978, my wife and I bought a 190-acre farm near Ithaca, New York, consisting of an 1840s-era farmhouse, a barn, pastures for our horses, lots of room for vegetable gardens, and a sizable woodlot for our wood heater, which backs up an oil-fired boiler and gas furnace. The farm was a great place to raise our kids; gives us a sense of security in an uncertain world; and allows us to be closer to the land and its resources.

Weaving Wind into the Energy Mix

Our loads were fairly typical for an older home. While we did not do a comprehensive energy audit and efficiency upgrades, we focused on the biggest energy load—heating. I redesigned our heating system to provide comfortable temperatures to fewer rooms. And we added a lot of insulation and then hired a local firm to add even more insulation to replace the vermiculite in the walls that had settled.

A few years ago, Art Weaver, an installer and builder of wind turbines, came to our place. We sat on our deck and watched the leaves blow in the wind as he told us about the benefits of wind energy. We seemed to have more wind than most of our neighbors because of our hilltop location.

Our home is grid-tied, but I was concerned about the security and robustness of our nation’s electricity grid. I wanted to be as prepared as possible for outages, and installing a wind-electric system seemed a good way to diversify our energy sources for greater protection against utility failures.

Art studied the wind, topography, and surrounding trees, on which he based the tower height. A tower height of 120 feet was chosen, to raise the turbine 30 to 40 feet above mature trees in the area. This height gets the turbine above the most turbulent boundary layer and into much smoother winds. Smoother winds mean less turbine yawing—with less yawing you increase energy production and decrease wear.

In June 2013, the Weaver 5 wind turbine began producing energy. I read the meter faithfully and could see that it was going to fall short of our consumption, which hovers around 20 kWh per day. The daily wind fluctuations didn’t surprise me as much as the seasonal changes did. I decided to add solar-electric modules and batteries to the system to further decrease dependence on fossil fuels—a key goal.

Pairing the PV Array

I wanted enough renewable electricity to be self-sufficient in the event of a lengthy grid failure, without having to resort to fossil fuels. This meant an allocation of at least 5 kW of PV to supplement wind for household consumption, and a little more than 5 kW of additional PV for the charging our electric car, a Nissan Leaf.

The wind system was originally a batteryless grid-tied system, with 3 kW and 7 kW SMA Windy Boy inverters. The 3 kW inverter is used at lower wind speeds (lower start voltage) and the 7 kW is used at higher wind speeds (higher start voltage). The addition of an 11.4 kW PV system, along with whole-house battery backup, required that the wind system also be able to charge the new 15.4 kWh lithium-ion battery. The solution was to AC-couple the SMA wind inverters to the AC load port of a 10 kW Princeton Power Systems DRI-10 inverter, which is able to accommodate a high-voltage lithium-ion battery. The PPS has four bidirectional ports—two DC ports (used for PV and battery) and two AC ports (used for grid and load). The Weaver 5 wind controller was also upgraded (by the manufacturer) to sense battery and load status in addition to grid status, and to safely control wind turbine output according to the availability of these loads.

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 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

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