Power Up Renewable Energy Co-operative

Welcome to PURE

Community-Based Sustainable Energy Strategies for Dufferin County and the Headwaters Region

PURE "Know How"

This page will serve as an entry point to PURE's collection of "How-To" information resources.

Got Wind?

On January 15th, 2005, PURE and the DCMA, Dufferin County Museum and Archives hosted "Wind Power on Your Property", a 2-hour seminar featuring the very much in-demand Dr. Jim Salmon of Zephyr North, who has over 15 years of experience in providing wind resource assessment services to the energy industry.

Dr. Salmon’s technical and informative talk illustrated the major factors for site selection and wind measurement in preparation for any wind power project, large or small. Dr. Salmon also talked about the interpretation of data collected from wind monitoring towers and equipment, costs, pitfalls, and spent a few minutes outlining the steps one needs to take to assess a local wind resource, using the Museum itself as a "ground-zero" example.

The event was packed to capacity, over 100 people attended, and PURE sincerely regrets having to turn away a large number of people who had hope to get in and hear the talk. We encourage all those interested in keeping up with developments in the wind industry and those doing their own wind power investigations, to join PURE, and stay tuned for our next educational event. We hope we can repeat Dr. Salmon's talk, or something similar in the near future for those who missed out!

Wind Talk - Review - by Richard Procter

Here's what I took away from the excellent talk by Dr. Jim Salmon of Zephyr North, at the PURE public meeting on January 15th, 2005. Basically, there's a lot of math involved, and numerous things to consider when trying to obtain power from the wind. Here's the main formula used to calculate wind "power density", a critical measurement when analysing your power potential:

Power Density = 1/2 × (air density) × (wind speed)³

What's important in this formula are the relative terms. Note that power increases linearly as air density rises, but increases geometrically (cubed) as wind speed rises. So double your windspeed, and your power factor increases by 8 times! A small, sustained windspeed advantage, gained for example by a higher tower or better location, could make all the difference for commercial success. As well, air density apparently can vary by as much as 40%, depending on temperature and pressure. Cold winter winds are much better than summer breezes.

Our formula can be expanded:

Power = 0.5 x (air density) x (wind speed)³ x (rotor area) x (various efficiency factors)

Those factors include things like generator and gear-box efficiencies, but note the other term. As rotor area increases, your power increases in linear fashion too (eg. double the rotor area, double the power). And don't forget that a wind turbine's rotor area is a function of the square of the blade radius, so double the radius, and you quadruple the area!

Anyway, enough math. The other factors that Dr. Salmon talked about included topography and surface roughness. Smooth, like the surface of a body of water for example, is way better than rough, like a village or forest. This factor can affect your power capture by quite a bit, and explains why the best sites for wind farms in Ontario are near or in the Great Lakes. Obstacles, such as barns and trees, can be critical for turbine placement, so stay away from these if possible.

Topography takes into account such things as hills and valleys, slopes and ridges. Locating on a ridge which is perpendicular to the prevailing wind is usually best. Ridges are better than hills, because the wind can't just flow around them. Moderate slopes facing the wind are good too.

Dr. Salmon's talk then covered numerous details about measuring the wind at your site using sophisticated towers and monitoring equipment, more work perhaps than most people are prepared to do, but essential if you are considering a commercial operation. Some better wind maps and data are becoming available from government sources, and several books are on the market to help the do-it-yourselfer in this process. Author and wind advocate Paul Gipe, for example, has published two excellent books on wind power- check out his website: www.wind-works.org for details.

PS. for further info, visit Dr. Salmon’s Zephyr North website, at: www.zephyrnorth.com

windrose A "wind rose" diagram illustrates windspeed and direction over time.

Do The Math! - by David Lutka

RETScreen: New Tool for Project Analysis

After looking into various renewable energy projects I soon came to realize how much work was involved in trying to calculate and justify their expense. Collecting all the necessary information and tailoring it to my specific goals was difficult and time consuming. Fortunately, Natural Resources Canada has developed a free and extremely comprehensive software system to ease this task, called "RETScreen", a case-study-based tool that helps any project planner better analyze the technical and financial viability of potential renewable energy projects.

RETScreen helps to determine if Renewable Energy TechnologieS (RETS) are viable at the critically important planning stage.

Formally, "RETScreen International Clean Energy Project Analysis Software" is available via the internet and CD, and is a unique decision support tool developed with the contribution of numerous experts from government, industry, and academia. The software, provided free-of-charge, can be used world-wide to evaluate the energy production, life-cycle costs and greenhouse gas emission reductions for various types of RETS. The software also includes product, cost and weather databases; and a detailed online user manual.

RETScreen can significantly reduce pre-feasibility costs. Renewable energy topics include:

Wind EnergySmall HydroPhotovoltaic (solar electric)
Solar Hot WaterPassive SolarBiomass
Ground Source Heat PumpsSolar Air Heating 


and RETScreen software also provides:

  • Product data, with over 1000 suppliers represented
  • Weather data from over 1000 ground stations
  • Satellite-derived surface meteorology and solar data
  • Background on the different technologies, with over 50 international case studies of real world projects
  • Greenhouse gas emission info
  • Financial analysis calculations

Training and technical support is provided by an international network of certified RETScreen trainers. Version 3.0 upgrades include a metric/imperial unit switch; updated product data; an enhanced GHG model to account for the emerging rules under the Kyoto Protocol; and a new Sensitivity & Risk Analysis worksheet. The Wind Energy and Small Hydro Project Models are now available, with the other existing technology models to be upgraded. RETScreen now has more than 48,000 software users in 202 countries around the world and is growing at 200 new users every week.

Need more help with RETScreen? ....see below

!! PURE Members Benefit !!

The RETScreen software can be downloaded for free at www.retscreen.net. But if you have tried the software and are having trouble or if you are just interested in having a potential project assessed, PURE's own David Lutka says he may be able to help out. David has taken the RETScreen training program and has worked through many of the case studies. He can be reached at dlutka@primus.ca, or 519-941-0642.

Back to the Future: Micro-Hydro - by David Lutka

Hydro power - generating electricity or mechanical power by putting falling water to work, is as old as the hills. These hills in fact, in Dufferin County and the Headwaters area, were colonized and developed more than a century ago in large part because rivers provided abundant power for milling operations. Towns such as Horning's Mills, Alton, and Orangeville itself were once power centers where early industry thrived.

Micro-Hydro, electricity created by falling water on a small scale, is still worth investigating, especially if you have a river, stream or waterfall on your property. The basic idea is to divert the flow of the water through a penstock (pipe), causing it to spin a small, highly-efficient turbine which then generates electricity.

Unlike wind that comes and goes, or the sun that sets, micro-hydro sites usually supply power 24 hours a day. A smaller amount of power over a longer period of time may equate to more power than a similar investment in photo-voltaics or wind. A typical PV array for example, rated at 1000W of output power, will generate about 5000W of energy over a five-hour day of strong sunlight. A small 200W hydro turbine operating 24 hours a day would produce almost the same amount of power.

The key parameters in evaluating a micro-hydro site are "head" and "flow". Head is the vertical height the water falls over the length of the available river run. Flow is the volume of water, usually expressed in gallons per minute, cubic feet per second or cubic meters per second. When flow and head are integrated mathematically, power is the result, usually expressed in kilowatts or horsepower.

A site with high head but low flow produces the same amount of power as a site with high flow and low head. For example, a site with 100 feet of head and 2gpm of flow will produce the same amount of power as a site with a head of 2 ft. and 100gpm of flow.

Low head sites are usually known as "run of river" sites. They typically operate with anywhere from 2 to 10 feet of head. For what they lack in head they make up for in volume. Run of river refers to a site where the flow of water is not interrupted. No dams or other obstacles are placed in the river to impede flow. This setup is considered to be relatively enviro-friendly and therefore may qualify for government credits.

To determine whether you have a suitable site, it is necessary to evaluate the available resources. Head, flow at the intake, penstock design and electrical transmission distance have to be determined as follows:

Head can be measured by taking the difference in height of the river at the water intake and the turbine. Flow is a little harder to determine. The easiest method to measure flow is to use the weir method, which involves channeling all the water temporarily through a barrier (eg. wooden dam) with a measured gap. Measurements should be taken throughout the year to determine your usable minimum and maximum flows.

All hydro systems require a penstock. A penstock is a pipe that runs from the intake down to the turbine/generator. It is important to use the right size and type of penstock to minimize flow restrictions. More power can be obtained from the same flow using a larger pipe due to reduced wall friction. Pipe size must be optimized based on costs and installation restrictions. Will the increased cost of a larger pipe be recovered with the increase in power generation, for example? As head decreases, so does efficiency. Keeping head loss low means that you maximize your power.

Once your micro-hydro turbine generates electricity, transmission losses may be an issue. As a general rule of thumb, the shorter the electrical transmission distance - the less the power is lost. For a site far from you house, transmission losses may be significant. Also, the larger the gauge (thickness) of wire the less the line losses will be. Costs increase with wire gauge however. Also, increasing the transmission voltage can reduce line losses.

Having determined the head, flow, penstock and transmission issues for a given site, the question remains, is this a viable micro hydro site? Factors such as generator selection, government approval, financing, construction and engineering costs must also be considered. Predicting the future cost of electricity will also be a key factor before you invest in micro-hydro.

PURE Members: PURE's David Lutka is available to perform a Retscreen feasibility study on your potential micro-hydro site. He can be reached at dlutka@sympatico.ca

Power Up Renewable Energy Co-operative
Dufferin County and Headwaters Region