Wind Turbine Buyers Information

I have been meaning to write this for quite some time. I think many people will find it useful because there is a huge amount of misconception about what wind turbines can do and what they can’t do, so before you go wasting your money or setting yourself up for disappointment please give this a read.

For our international readers please note that what is written here is globally common so although I may make reference to South Africa the actual content holds true for all wind turbines regardless of your location. Also, the wind turbines I am referring to here are domestic/light commercial class wind turbines, so that’s pretty much everything from 300watts to 10kW either horizontal or vertical axis (I will explain the difference).

I come from a true renewable background. By this I mean that I am experienced in numerous technologies associated with renewable energy. Now this may sound like a casual statement but there are actually not many of us here in South Africa mainly because few people were stupid enough to try and sell renewable energy products before it was financially viable. I always say to clients that you can tell the age of a renewable energy company by their product grouping. Companies that primarily sell solar (PV) systems are generally start-ups without long experience (relatively) in renewable. The reason I know this is because true renewable companies started in a time that the cost of a solar panel per watt was around R63 ($5.25) and the only people that ever bought them were extreme tree huggers and high sites that simply had no other choice. This meant in order for us to stay alive as a company we had to sell technologies that had some semi semblance of financial practicality. Enter micro hydro turbines, wind turbines and to a lesser extent gas turbines, but so as not to digress I will stick with wind turbines in this article and cover micro hydro turbines in another article.

Selling wind turbines is a hazardous business primarily because people don’t understand them or rather have false expectations of them. I will address these first so as to inject the basics.

Type of Wind Turbines and Why?

The most commonly sold wind turbine in the world is horizontal axis, the reason for this is that they are simply more effective as they front up with the wind and produce power with greater efficiency per swept area. In the picture below you can see a horizontal axis turbine, the horizontal part is that the head and internal generator are horizontal to the ground. Swept area is the total reach of the blades from tip to tip.

Horizontal Axis Wind Turbine
Horizontal Axis Wind Turbine

The problem with horizontal axis turbines is that they require clean wind in order to operate at their greatest output and since they are installed low on the ground, typically 6 – 12m,  the air can get extremely turbulent do to any multitude of obstacles obstructing its free movement. Turbulence can cause the turbine to lose its track out of the wind and reduce power as it does so. This can be seen by the wind turbine being unable to stay on a single line against the wind and instead keeps turning away.

Manufacturers of wind turbines are well aware of this problem and have come up with various methods to reduce the effects of turbulence or dirty wind on the turbine. Common mechanical methods are long angled tail turbines (very common) and computer vane-controlled turbines (mainly in large units) but another way to completely overcome the problem is by using vertical axis turbines.

Vertical Axis Wind Turbine
Vertical Axis Wind Turbine

These turbines have a dramatically reduced impact by turbulence since they spin on a vertical plane (angled up from the ground) and thus can convert both turbulence and multidirectional winds into useful wind for generation. This may seem like a logical step, but vertical axis turbines pay a price of lower rotational speed since they are not fully fronting up with the wind. In addition to this the swept area of the turbine needs to be significantly greater because there is less direct energy being transferred to the heads internal generator. Finally, since demand for vertical axis turbines is lower the cost of buying in a unit is that much higher.

Why do I provide you with all this information? Because clean wind is key to good generation for almost any type of wind turbine. That means as few surrounding obstacles (trees, buildings, towers, mountains etc) as is possible, and if obstacles are unavoidable then as far or high from them as you can possibly can. Don’t go thinking you can install a turbine in your backyard that has a tree line between the turbine and the predominant wind, you just asking for frustration.

Wind speed and Frequency

Wind turbines are normally rated (watts or kilowatts) at wind speeds of 9m (29.52 feet) per second which amounts to 32.4 kmh (20.13mph). As an example, a 1kW wind turbine is rated as 1kW in 9m/s wind speed. This is no joke for two reasons. First, a wind turbine rated at 1000watts requires a persistent wind at its rated speed to achieve 1000w. This must not be interpreted as a sporadic wind gust at the rated speed, it quite literally means a wind turbine not turning away from the main stream of wind (turbulence) and that main stream of wind persistently flows for 1 hour at the rated wind speed. This happens relatively infrequently even on the best wind sites and if it does, it’s for a couple of hours and certainly not for 24 hours. To put it in a more natural perspective. If you are driving down the road at 32kms (20mph) and you put your hand out the window, the wind resistance you feel on your hand would need to remain like that for 1 hour just to achieve its rating of 1000watts.

Again, wind turbine manufacturers are aware of this and for this reason they focus on the start up wind speed which can vary between generator types, makes and sizes but is generally accepted at around 2m/s (7.2kmh/4.5mph). Below you will see a graph. This graph is common with wind turbine spec sheets as it reflects the power generation at lower wind speeds. As you can see the power generation stays relatively low at low wind speeds and only as it nears its rated speed does it take a steep climb.

Wind Turbine Power Curve Graph
Wind Turbine Power Curve Graph

What does this mean? It means at lower wind speeds you are generating power but not much power relative to the rating of the wind turbine. It means that when you are standing on your patio and feeling a stiff breeze on your face that that breeze may not actually be sufficient both in terms of wind speed and in terms of clean wind.

Naturally frequency of wind is also important. If you do feel a breeze on your face while standing on your patio how often does that happen? Does it happen every day? Every month? Is it seasonal? If the wind does blow every day, how long does it go for and at what speed? All of this information is what you should be collecting to start building up your decision to buy in a wind turbine. Remember that merely because you notice the wind does not necessarily mean it has a frequency that will make it a viable investment both in terms of cash and in terms of energy.

Big turbines and protection

Many clients staying in rural or open suburbs often approach us to buy in 2kW or greater wind turbines. I tell them no. Why? Because in suburban type areas even with big yards wind turbines can be scary. Really scary.

A small 500watt HM class turbine has a swept area (spinning rotor diameter) of 2.5meters/8 feet. This swept area increases as the wattage increases. By the time you are at 2kW your swept (depending on make) is at 5meters/16 feet. This is all fine and well when the wind is low or average but when the first storm front strikes with gusting wind speeds nearing 80-120kmh/49-74mph a turbine standing at 9-12m/30-40feet (near the top of your house) with blades spinning so fast you can’t see them takes on a wholly new meaning, if not to you, to your neighbours. Your mind will drift back to every bolt you tighten, every blade you fixed and the cable you ratcheted tight. This is even harder for those people who never installed it themselves.

Ironically wind turbines are designed to accept this kind of punishment. They are tested up to 180kmh/111mph. They will really be okay in pretty much anything outside of freak storms that would take your roof off anyway. Most turbines have built in protection mechanisms that turn them out of the wind in extreme weather, they stop generating power or choke back power and either lift vertically or turn horizontally. Still doesn’t make it a pretty sight for you the homeowner.

Installation procedure and maintenance

Installing a wind turbine is no simple task and requires planning. When you get your turbine its not merely a matter of putting it on the pole and lifting it. You need to remember that the turbine will be up there for quite some time and some tricks can really make it a great success or huge irritation. Take the time to sight it properly. Look at the area carefully, watch it for a few weeks, see where the wind is coming from and how its moving. Clear if need be.

A guy wire turbine requires a super powerful centre that must be perfectly level. This is the one important part of the mast installation. A level centre with a good foundation and super strong concrete/ guy wires. Always error on the side of caution when sinking your base plate hooks into wet concrete. Grease your turbine at all joints with generosity. This grease will protect exposed bolts and joins from the weather.

While on this subject we commonly have requests as to whether turbines can be mounted to a building/home. The answer is yes if your turbine is really small (think Air X) but no if you are looking at large turbines in terms of physical size or rated wattage. Just to be clear, you can mechanically affix it to your house but very few things will stop the vibration down the tower and into your walls.

So wind turbines don’t work?

  1. Of course the work. All I am trying to do with this article is instil in potential buyers a sense of reality that will improve their experience. Here are the first things you should do:
  2. Try and obtain as much wind information as possible. Check to see if someone has a meter station near you. If not, try the met office, if not the met office when driving about see if you can see any anemometers or wind vanes and ask them to share the data. The point is don’t merely rely on what you feel, try to obtain the data freely first. If you intend to buy a larger wind turbine, check online to see if you can cheaply buy a anemometer and wind vane. Place it roughly at the site that you intend to install in and meter the reading for a few months.
  3. Pick an area that has as much clearance between it and any obstacles as possible yet is in the main flow of wind. If necessary clear the area but don’t go overboard, no wind turbine output can justify cutting down a tree that’s been growing for 30years.
  4. If you have neighbours discuss it with them.
  5. Depending on the size of the turbine, check the ground for ease of installation. Plan it properly and step out the guy wire stay sites and main tower sites.

If you have done all of the above, send us or your local service provider all the information you can.

That’s it. I hope this article was not too long, ironically, I actually had to shorten it so as not to lose you. If you need any assistance, please don’t hesitate to drop me an email.

Jason Sole
















Solar Battery Buying Basics

So, you want to buy a solar battery but have no clue where to start? Need help in working out what’s right for you? Or perhaps you have an idea but dont know what all the terms mean?

In this guide we will take you through the basics of what you need to know before buying a battery, we will keep the information light but cover the important points:

How much storage do you need?

Simple question, if you know the answer you can just switch to our calculator here. If not, what you will need is an idea of how much power you are trying to store. You need to work this out in kWh (kilowatt hour) or if a small system, in terms of Wh (watt hour). If you are new to this concept or unsure, consider the following, note the bold text stating battery type:

Define your needs – What are you trying to do?

Go completely off grid?

  1. If you are going completely off grid then your battery becomes critical. It needs to not only store your daily consumption, but also needs to store days where your solar (assuming solar system) are underperforming due to weather. Some people try to offset the poor weather days by adding a small wind turbine to the system. As a concept this is feasible only if you are in a good wind region but for a number of people this simply isn’t an option.
  2. If you have no existing electricity bill, you will need to asses your off grid requirements by doing the horrible task of a manual energy audit. This is that nasty boring task where you write up your list of power drawing devices that you intend to add to the system. The format is best done on excel for easy calculation like in our Energy Assessment Calc Sheet. The objective being to tabulate your worst possible consumption scenarios and design from there.
  3. Another design consideration is whether you have access to Eskom/Utility/Generator but are choosing not to use it. At present it is still cheaper to utilise either of these resources as a back up to days without good energy generation due to weather. Thus even though you may be able to size bad days these into your battery bank, you should consider to rather use existing linked sources.

Go Partially Off Grid?

  1. Everything starts somewhere. This system typically is designed to keep your power bill down by utilising the PV/Wind sources during daytime for both power and charge, it will also have a small battery bank on it to lean on in the event of a load shed/power interruption. The difference with this battery system and a typical load shed or UPS style system is that it is designed to power your entire load. Commonly the battery will form a part of integrated use, meaning that its cycled daily on the system. Battery requirements are generally larger but unlike an off grid system power sources are freely available between Eskom/Utility or RE power source.
  2. So how much power required on store? Generally speaking you would do one of the following things:
    1. Use an Energy Owl or other power meter to determine hourly consumption. Then calculate the number of hours you would want to be on battery in terms of kWh.
    2. Use your electricity bill as a guideline. Either take the entire electrical load for the day (meaning an entire day on store) or take a partial amount by roughly calculating the total days kWh and dividing it by number of usable hours in a day. i.e. Not 24 hours because you sleeping most of it, use 12 or 16 hours. Its entirely up to you.
    3. Experience guideline: A house using 25kW per day is right at the top end of what is financially feasible for a battery system. Naturally you can power any amount but its far easier and cheaper to reduce your power via solar geyser, some LED’s etc. Alternatively use your PV during the day to reduce your bill and add on a decent sized battery system to take care of power outs etc.

UPS or Anti Load/Power Shed System?

  1. Maybe the most commonly bought system in the entire country during the 2015 blackouts.  This system typically will power targeted systems? Lights, TV, Alarm or will cover at least 2 – 3 hours of total load. In some cases the system is cut into the DB board, in others it’s just an inverter with a battery and an extension lead covering a single place in the house.
  2. To size this system you simply need to determine the number and power consumption of the items added to it. You can use the Energy Assessment Calc Sheet to work this out. Remember a system like this is not designed to power the entire house, if it is then you should be looking at a partial off grid as above. These systems are typically target orientated.

SUMMARY – First select the type of system you want. It’s the first step in selecting the battery type and characteristics. Remember, once you have your total storge requirement you can just jump over to our Solar Battery Sizer and it will do all the work for you.

 Battery Types and Characteristics

I am going to break with norms here and talk plainly. The internet is rife with in depth articles regarding batteries, so the objective here is not to repeat that but rather to put the important terms in human language. On the previous page I mentioned SUGGESTED BATTERY TYPE. See below:

Battery Type 1: 1 – 2 Year Battery

This battery is your typical cheap lead acid class battery. They come in numerous shapes and sizes but in general they are rated 100Ah, 105Ah, 120Ah, 200Ah and 230Ah. Their brands are Excis, Narada, Maximus, Deltec, Royals etc. Do not get your expectations up with these type of batteries. They do the job but nothing more. Since batteries of this type of used commonly in UPS or Load Shed systems its important to look at the C Rating. C Ratings are the rating at which a battery will give up power over a specific time period. Hence a 100Ah 12v C20 rated battery is designed to give up 100Ah over a period of 20 hours. This may not work well for you, as its short term requirements may beep out the inverter when it demands more than the battery is capable of yielding. Try to work out your system bearing this in mind and ALWAYS check the C5 (5hour) or less rating for best results.

Battery Type 2: 2-3 Year Battery

This is a very narrow band of batteries currently occupied by the Trojan non RE class battery or entry level Lead Crystal and early SonX Gel/AGMs.

They are a good battery, but cycled to 50% the life span just doesn’t have the legs. They do much better when cycled to 30% (my preference) but generally systems and budget limit this option. Typical sizes for this are 150Ah, 180Ah, 200Ah, 225Ah and some 250Ah although the AGM/Gels start at 100Ah, voltages vary between 6v and 12v. Most golf cars make use of this type of battery.

Battery Type 3: 3-5 Year Battery

You have now entered the domain of the true renewable batteries. This is all the Trojan RE/T20 batteries, your Omnipower (on the lower side) and Sonic (on the top side). Although batteries like this start in 100Ah generally most people buying this are going for the larger 200’s or 250Ah, the Trojan class will push these right up 820Ah but pricing starts becoming a little silly.

They are good, durable and can take a real pounding. Excellent recovery windows and long float lives.

Battery Type 4: 8-12+ Year Battery

These batteries are typically 2v cells assembled to whatever your voltage requirement is. In this class is also the LifePO4 and the famed Tesla battery. You do of course get 12v LifePO4 but at the time of writing this the pricing makes the LifePO technology rather stupid. It would be far smarter for you to buy in cheaper batteries and wait for the economics of scale to play a role than invest in LifePO technology. Tesla may be a great brand and if you have money to waste then it may be what you are looking for but alternatively should you want to buy smart than go with the 2v cells.

Typical brands that are notable are Willard RTs, Deltec XILFs, Raylite M classes and Hoppecke. They are all expensive, the list was in a way put in financial order. Even though they require maintenance and some TLC they really really last, if you have the spare cash they make an excellent buy.

Notes and Terminology

Battery C Rating – This is the rate, expressed as a time (usually hours) that a battery is discharged relative to its maximum capacity. You need to start looking at this when buying batteries because aside from the technical implications, many salespeople will fool you into thinking you are getting more than what you are paying for. A good example of this is the Omnipower 260Ah. It’s rated at C100, meaning that it is designed to yield 260Ah if drawn over a period of 100 hours. Your invoice will reflect Omnipower 260Ah and you will think you getting quite a bit of juice(power) but its rating in a renewable energy system (C10) is actually 200Ah. Big difference when you consider what you paying for it.

Battery Types – There are many batteries not mentioned here. I actually felt quite bad leaving them out. Batteries like U.S Lead, Sonneschein etc definitely worthy of mention but I am focusing on commonly used low cost batteries or high volume batteries.


I hope that I have managed to assist you in some way. The important part is determining your needs in terms of what kind of system you are trying to build. Then working out how much storage in terms of kilowatt hour that you need. You can then jump over to our solar battery sizer to work out the amps and other factors. Once completed, take a read through the Battery Types, take in a few of the names and start hunting around for prices. Good luck:)

Free the Grid – The Great Solar Rip Off

We are being misled by the Minister of Energy, Eskom and the entire IPP program. Today we were informed that a 100 megawatt plant cost them 62 billion rand. Sadly, this is probably true. BUT. The reason why it cost so much money is due to the very people that are now complaining about the cost of it and even worse, using it as platform to justify the use of nuclear power.

Here is why.

Eskom has stalled signing a power purchase agreement citing increasing costs (see: ) . They are correct in their assessment regarding the pricing of the project and the overall net cost to consumer/eskom over the course of its proposed 20-year life span. They state that the project will cost consumer/eskom 62 billion rand. 62 Billion Rand?? The numbers are simply ludicrous. Yet Eskom not only is compelled to basically sign off on it but in addition to which has signed off on many similar deals. How is this even possible? How is it possible that a solar plant and its intended output could cost so much?

I am in the solar business. Frequently I get requested to design solar plants from 10kW through to 150mW. I am completely in touch with pricing regarding hard equipment costs and installation costs. So to put you in perspective. Even on a retail level, the cost of 100mW, with top end equipment, on current exchange rates and fully installed with generous income figures costs only R1 958 692 149. In a nutshell. It costs R2 billion rand. This means that you could build one new plant every year for 62 years and it would cost what they are being charged for a single plant. Bare in mind also, that the cost of power production is free since it is powered by the sun. Add to that some ongoing costs for maintenance and cleaning, it in no way does it come anywhere near the figures been proposed by Eskom. So how did we get into this position?

It all started when the IPP programme was first created. Some geniuses came up with the application vetting process. You had to pay R15 000 just to download the documentation for bid submission. Once downloaded you were met with an onslaught of regulations and requirements. The few big problems with this document became immediately apparent. First. You had to have experience in similar scale projects. Now think about that. This is the first project of its type ever in this country’s history and yet, you had to have experience with these projects. Immediately almost every South African company that once celebrated the launch of the programme was discounted from participation completely. Second. The government did try to include South African companies by forcing local content requirements. This itself was almost farcical. There has never been a scale photovoltaic manufacturer in this country that was 100% South African owned, ever. All plants locally are assembly plants and foreign companies. The same is true for the inverters, there is zero scale manufacturers locally. Finally, perhaps been aware of the document shortfalls they included a BEE (Black Economic Empowerment) component. This was partially successful but the aforementioned criteria meant that they were getting a tiny segment of its true potential. Third. The financial modelling requirements and engineering requirements placed on each potential plant by the government meant that only seriously large engineering firms could really participate. Again another blow to the local industry. Fourth and finally. The cost just of the submission process, with its requirements for EIA approvals, grid proximity, permissions, financial modelling, engineering designs meant that the cost, aside from your downloaded documents (R15k), were so ludicrously expensive that only foreign banks, some well-connected local banks and extremely wealthy individuals had the resources to pay all the costs and gamble on getting nominated as a winning bid.

I still recollect going to the opening of the IPP program at a launch at Gallagher estate in JHB. On arrival the first thing that struck me was how many foreigners there were. It was like a Turkish bazaar and huddled in a small group standing in the corner were literally a handful of South Africans. I still asked the NERSA representatives what the point was of making a programme that no South African could really participate in. No answer.

So, along with a document like this we need to make some concessions. There is a legitimate requirement for safety both in power production and in stability of the grid. There is also a need to have certainty that what you are buying is going to work and has some beneficiation components built into it with all the correct permissions. However, not in the way this was done and not to the detriment of all electrical consumers and local firms. All this has achieved is a negative view on solar power being costly and created a basis on which our minister can drive in nuclear power.

How should this of been done?

Simple. Eskom builds its own solar plants. I know right. Sounds crazy but if they didn’t outsource this requirement to fat wealthy foreign companies and businessmen, we wouldn’t have found ourselves in this position. Why? Because I am stating a fact. It is completely factual that 100mW of solar power should only cost 2 billion rand, we are paying more because we have been ripped off. Eskom could have saved PLENTY and would have been able to benefit local communities for cleaning and maintaining the systems thereby creating work NOT benefits. Even if the system underperformed there is no substitute for FREE electricity. It’s free. No input costs of coal, uranium or natural gas, it makes power every day the sun shines. It is mathematically mind numbing that you could even for a second believe that any other type of power type could ever be cheaper (or faster to build) then renewable energy because it has none of the aforementioned costs. In an ideal world. We would do the following:

Build our own solar panels. Most local companies import from Q Cell in China and assemble so why not make a South African solar panel, call it sunshine in whatever language you like and create a local industry. Then, direct investment into local inverter manufacturing firms, firms like Microcare SA or MLT Drives and get them to scale up operations and create grid scale inverters. They have such brains behind them it’s ludicrous that they are dredging in the back waters behind all this imported product. More importantly they employ local people already by the arm load and would need to employ thousands more to keep up with the demand. Then stop exporting our freaking copper to China and manufacture locally, also manufacture solar cable, mounts and connectors. It’s really not that hard. We are not talking about splitting an atom, we are talking about stranding wire. Then free up the grid. Stop trying to tax local consumers with petty income derived from the sale of electricity. Allow consumers to put power into the national grid with safety standards in place but no requirements for net metering or ongoing costs. If the value of generation from solar power sources surpassed grid demand, then allow them to keep it for free. You do not have to pay them out. You just have to allow them to offset their bills. Most importantly. Should any of this idea be adopted and Eskom finally wakes up to the power of renewable energy. I only then ask that they stop charging consumers for power that they obtain freely from the sun/wind/ocean. They can charge a rate for maintenance but let the consumer enjoy the benefits obtained from free power. Money left in the consumer’s pocket stays in the economy and more importantly provides a break for companies that are already reeling under electricity costs.

If that sounds crazy to you lets just bare in mind that Chile generated so much power from their RE systems that they gave their citizens in some areas free electricity for roughly 192 days, almost two thirds of a year. ( ) Their problems are slightly different now as a result because albeit that some consumers got cash windfalls, the developers of those plants are struggling to get a return on their investments. For this reason, we need to completely exclude middle men or third party suppliers and do it directly as a national project.

If the concept of free power is not sufficiently enticing to you then consider this. All forms of fossil fuel power generation require water. This in a time when farmers are facing massive losses due to drought ( and the department of water affairs estimates that we could be in serious water crises by 2030. Is this really responsible? Especially when you consider the impact that the latest coal fire plant Medupi is going to have ( . That’s an astronomical amount of water that could be utilised for the production of food/drinking water, but instead will get spent on power generation. At present the water consumption average for all power in South Africa is roughly 1.32Litres per kilowatt hour?? In other words, they utilise more water to generate power than the power they produce, take a look at a production graph from Eskom themselves:

Link to Eskom Water Statement

If you are unimpressed with the water argument what about CO2 emissions? In a time of world uncertainty regarding climate change, our agreement to the global carbon emissions protocol, our implied carbon tax that looms over the horizon. How on earth could we even consider other types of power sources. At present, Eskom produces power at 0.99 kg of coal per kilowatt hour of energy. Think about it. That’s 1.32L of water and 0.99kG of coal just for 1 measly kilowatt hour of electricity.

For those of you thinking that nuclear is a better option because it’s cleaner. Let me assure you that, albeit that nuclear is in fact cleaner in the way it produces power, it ceases to be cleaner when you incorporate the massive levels of CO2 emissions generated both with the mining and transporting of uranium. Then if you also take into account the absolute wasteland created from their water emissions and the unavoidable mess of nuclear waste disposal, I question myself how on earth it’s possible that we could even consider any other source other than RE.

I hope that I have not bored you with this document. I will be more than happy to supply you with source documentation on costs of solar plants down to current quotations received for the imported equipment. Solar power is not a scary creature of science; it is a simple mechanical truth that has for too long been over engineered. There are countless local systems already feeding into the grid. Systems put up by the average man. It does not require some massive degree of genius to achieve why over pay for it, FREE THE GRID.

Jason Sole – GW Store Renewable – Mother Channel –