Advice from an Expert - Environmental Benefits of Your Wind System

ADVICE FROM AN EXPERT
by Mick Sagrillo

THE ENVIRONMENTAL BENEFITS
OF YOUR WIND SYSTEM

A resurgence of renewable energy installations is occurring across the country. This phenomenon is driven by a variety of factors, for example:

- Serious computer users, who do not like the momentary power line flickers that seem to occur with greater frequency than in the past, are installing uninterruptible power supplies (UPS) between their computers and their utility. Many of these UPS systems are supplemented with renewables.

- For some, Y2K worries loom as a serious threat to reliable electricity supplies.

- Also, professionals and others who can earn a living with a computer and telephone are moving to the woods and fields. Many are building houses that are distant from the nearest power lines, and they turn to renewables as a source of electricity when they hear the price of the utility’s grid extension. Having moved to the country to increase their quality of life, they do not even consider a gas or diesel generator.

Anyone fortunate enough to have a stream on their property soon learns how to gently harness hydropower. Others turn to wind generators or photovoltaic (PV) arrays to electrify their homes. Unlike a good hydro site, off-grid wind or PV installations need a backup source of power because neither the wind nor the sun can provide 365 days of electricity at an economically reasonable cost. PV installers are discovering today what wind installers on the Great Plains learned half a century ago; you need to rely on a gas generator for the sun-impaired season.

When PV panels became more moderately priced, off-grid wind installers began specifying them for their systems. Now, even PV installers can recite the adage, "When the wind doesn’t blow, the sun shines" (and vice versa).

A wind generator, tower, and long wire runs are still more cost effective than a comparably-sized PV array on a non-movable fixed rack, by a factor of two to three. As a result, sizing of the two generating sources becomes a function of how much of each resource your site enjoys. For the most part, how much wind and how much PV to install depends on the area of the country you hail from.

The extreme southwest corner of the United States does best with half of their generating capacity in PV, and the other half in wind. In the extreme southeast, where the only winds are associated with hurricanes (too much fuel), wind generators are not even an option. The other 90% of the country can safely size wind/PV systems by putting two thirds of their needed generating capacity in a wind system and the remaining one third into PVs. This ratio is largely based on the economics of the two generating sources versus electricity generated, trial and error by many installers, and what works.

While a wind/PV hybrid system will be slightly more costly initially than either system alone due to the added generating capacity, there are some money-saving advantages.

First, the wind system or PV array are sized for their respective peak generating seasons rather than their worst seasons (summer for PV and winter for wind). Since the spring and fall enjoy both resources, they complement each other quite nicely.

Another money-saving advantage of a wind/PV hybrid is that the battery bank can be smaller than what is required for a one-resource-only system. Batteries are usually sized for the worst-season scenario, which is virtually eliminated in a hybrid system. In a hybrid system, batteries are sized to maintain the system load for two to three days, about half of the five to six days normally planned for a PV-only or wind-only system. Battery capacity must also be sized to be at least six times larger than the maximum combined capacity of the wind generator plus the PV array.

Finally, the stand-by generator that is an integral part of any PV-only or wind-only system, can, for all intents and purposes, be eliminated, along with the fuel that was burned in it. In virtually all of the PV/gas generator systems where I have added a wind system, the stand-by genset is only run for 30 minutes every month for maintenance purposes. (This is done according to manufacturer suggestions to genset owners.) Many homeowners, after running their hybrid systems for a year to get comfortable with them, have opted to sell their gensets and reinvest the money in other system upgrades.

Hybrid system owners are some of the greatest renewable energy advocates. They reap the benefits of both the wind and sun. Their systems are cheaper in the long run and far more environmentally benign than reliance on a renewables system paired with a fossil-fuel genset.

-- Mick Sagrillo, Sagrillo Power & Light Co.

Back to: Advice from an Expert

Wind Energy FAQ | Publications | AWEA Home Page