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AdvancedSIMPLE CALCULATION OF YOUR OWN WIND TURBINEThe calculation of personal autonomous Wind Turbine is relatively simple if follow the instructions written below. NOTE: We purposely simplified some data, numbers and calculations as we understand that not all Wind Turbine users have technical background and can make complex calculations by themselves. Relative error in calculations does not exceed +/- 10%. 1st STEP ON THE WAY TO FREE POWER SUPPLY – WHAT DEVICES DO YOU HAVE? Find out from manuals the power consumption of all devices used at your home or location where the Wind Turbine will be installed. You can use the table of power consumption below. However please remember that these numbers are APPROXIMATE! In case you have a problem with calculations, ask specialist or technician. 2nd STEP – PEAK POWER CONSUMPTION CALCULATION Make your own calculation in parallel with our instructions. Calculate minimum and maximum (peak) energy consumption of your house. You can use the table of approximate values below:
In our case the “peak” or power consumption is about 12 kiloWatts (kW) during 1-2 hours per day – when all appliances are switched on. In real life such situation happens very seldom. Usually you switch on the electric kettle OR coffee machine for 5 minutes. As a rule nobody switches on microwave oven at the same time when he uses electric iron. Vacuum cleaner is never switched on simultaneously with hair dryer, etc. Even if power costs nothing, it’s no use to have all devices switched on, as they go bad with time. If you will consume energy reasonably, you can choose less powerful (and less expensive) Wind Turbine for your needs. For instance, you can first boil water in electric kettle, then switch on microwave oven, and then go use vacuum cleaner. This consecution of your action is logical and can be easily foreseen instead of buying more expensive Wind Turbine (12 kW power in our case) and only once a year use this big power during 20 minutes. 3rd STEP – HOW MANY KILOWATTS I CONSUME? Look at your Electric Company bills for the last 6-12 months. Find the maximum one and write out the number of consumed kiloWatts. Let’s say this number for average family of 4 people is 500 kW-hours per month (i.e. 500kW-hours / 30days = 17 kW-hours per day or average 17kW-h / 24hours = 0.7 kW per hour). It’s average power consumed by your house. For your information: Energy is the power consumed during one hour. The energy consumption is relatively low. However the problem is the peak power supply during morning and evening-night time, especially in winter when electric heaters should be added to the usual devices consumption. Gallup Poll of 1000 people, living in houses and apartments in central part of Russia showed that the average peak of medium apartments or house is a bit more than 3 kW. It can be proven not only by analysis of the number of devices at home, but also by the fact that most of the average apartments and houses have fuse box on 15 Amperes. It means that at 220 V voltage maximum energy consumption can be maximum 220V х 15A = 3300 W or 3.3 kW, otherwise the fuse will burn. You can also check your fuse box and calculate maximum possible peak power supply at you home. We calculated that the average energy consumption of average family of 4 people is 0.7 kW/hour, peak energy consumption is 3 kW/hour. 4th STEP – WIND SPEED IN YOUR LOCATION Inquire the average annual wind speed in your region from meteorologist or via Internet. Let’s say it is 6 m/sec (meters per second). 5th STEP – NOMINAL AND REAL POWER PRODUCED BY WIND TURBINE “Nominal power” generally shown by production company in technical characteristics, is determined on 11-12 m/sec wind speed, depending on different standards. Nominal power of Wind Turbines produced by SRC-Vertical, is calculated on 10.4 m/s wind. Everybody knows that it’s anyway very high speed of wind which is not available very often. For instance WPU-1 (1 kW nominal power) will generate only 212 W/hour on 6 m/sec wind. Thus in your region you need bigger Wind Turbine to produce 0.7 kW/hour (see step 3). In our case its power should be about 3 kW (see the table in “Information” - “Basic”). Simplified table of dependence of WPU-3 power generation on wind speed is shown below:
As you can see WPU-3 (3 kW nominal power) will generate 700 watt (0.7 kW) per hour on the average wind speed 6 m/sec. When the power consumption is low (you are out of home), Wind Turbine charges batteries which give out their charge during peak energy consumption (morning, evening). 6th STEP – MAKING A DECISION ABOUT THE SIZE OF WIND TURBINE If you don’t want even to think about saving money and spend money right and left, then bravely make a decision to buy Wind Turbine which generates 12 kW nominal power (in accordance with peak power consumption of your home). However it’s a premature, unjustified step leading to absolutely unnecessary expenses. And we will show why. This great power will be used during 1-2 hours per day and not every day. Do not forget that the bigger the Turbine, the more money you need to spend on purchasing and further servicing – Wind Turbine is as automobile, it saves your time and money, but requires periodical attention. If you are thrifty and don’t want to spend more money than it needs, let’s discuss the results we’ve got. 7th STEP – BATTERIES FOR PEAK ENERGY SUPPLY When electric energy is produced, it should be consumed immediately. It’s a physical law. It means that if Wind Turbine generates energy, but you cannot consume it, you should store it up. Instead to cover the short-time peaks of energy consumption you need some energy storage device which will be storing the energy during low consumption and giving it up during the peaks of high consumption. The sample of such device is regular automobile battery. Peak energy consumption of average apartments or house is about 3 kW (see step 3). This peak continues for 1 hour in the morning and for 2 hours in the evening. It means that during main peak in the evening the average consumer needs 3 kW x 2 hours = 6 kW-hours. Wind Turbine charges batteries between morning and evening peaks. To get 6 kW for 2 hours (see step 5), you need to have the stored 6.000Watt / 12Volts = 500 Ampere-hours. However you cannot use battery for more than 80%. So the real energy storage should be 500 Ampere-hours / 0.8 = 625 Ampere-hours. Efficiency of VDC-VAC inverter is generally 85%, i.e. the part of power will be spent on this device operation. So initially you need to have 625 Ampere-hours / 0.85 = 735 Ampere-hours. Regular automobile battery has 75 Ampere-hours capacity. It means that you need 735 Ampere-hours / 75 Ampere-hours = approximately 10 batteries. NOTE: the number of batteries should be divisible by 4 to get 48VDC output. So choose either 8 or 12. Or buy 8 and see may be it’s enough for your use. Do not be afraid of this number. First of all, it’s not a big deal – about 300 Euro – and you never pay bills for electric energy! The second – is that the volume is not so big, as it seems, especially when you are talking about a separate house. And the third – you can buy 1-2 big expensive batteries of the same capacity. On the base of these steps you can calculate the required number of batteries for your sweet home peak energy consumption. During the minimal consumption and windy weather (day and night) Wind Turbine will charge batteries. The speed of charging depends on the power generated by the Turbine, i.e. on the wind speed (see step 3 and table in step 5). You can easily calculate that WPU-3 (3 kW on 10 m/sec wind speed) generates 0.7 kW on 6 m/sec wind speed, or 0.7 kW x 12 hours = 8.4 kW-hours during the day time plus the same during the night. As you can see it’s enough for peak energy consumption. However everybody knows that there is no miracle and in every point of the Earth the wind is not blowing constantly. There are several windless days during a year. Of course, it’s not economically feasible to purchase the big Wind Turbine or big number of batteries for a few days in a year. For the most people the simplest solution is economical solicitous consumption of energy during such days. For those who doesn’t want to save, it is necessary to know the average (or even maximum) number of windless days in a year and calculate the required number of batteries. For instance maximum number of windless days during last 5 years was 5 days in summer when you spent 10 kW-hours per day (24 hours), and 3 days in winter when you spend 20 kW-hours per day. Of course you should take the winter period as the biggest consumable. So 3 days x 20 kW-hours = 60 kW-hours. To get 60 kW-hours (see step 5) you need to have 60,000 watt / 12 volts = 5,000 ampere-hours. However you cannot use battery for more than 80%. So the real energy storage should be 5,000 ampere-hours / 0.8 = 6.250 ampere-hours. Efficiency of VDC-VAC inverter is generally 85%, i.e. the part of power will be spent on this device operation. Initially you need to have 6,250 ampere-hours / 0.85 = 7,350 ampere-hours. Regular automobile battery has capacity of 75 ampere-hours. It means that you need 7,350 ampere-hours / 75 ampere-hours = approximately 100 batteries. As you can see this number of batteries will solve the problem of plentiful energy consumption, but will require bigger Wind Turbine for charging as small Turbine will not be able to charge quickly this number of batteries. Well, may be it’s better to live economically 3-5 days in year? It is necessary to note that batteries have a property of residual capacitance. Let’s say you use battery on 90 Ampere-hours. You switch on 1000W lawn-mower for 45 minutes, after that the inverter switches off by itself. You can reduce the loading to 500W (electric fret-saw) and use it for the same time. Then you can connect 300W drill, then 130W spray painter, then 60W soldering iron, and finally 30W bulb. But even in this case you will not “bail out” 80% of power capacity from the battery. 100% “bailing out” is not recommended as the life time of battery is getting down after such extreme use. This example shows that you shouldn’t switch on all your devices simultaneously. We recommend to buy servicing-free batteries as you wouldn’t have to check the electrolyte level and add distilled water. Just visually check batteries once a year. Traditional automobile acid batteries are widely distributed and less expensive, however require separate ventilating room, special servicing and cause untoward effect on humans and apparatus. The most convenient and save batteries (for indoor application) are absolutely service-free sealed batteries. 8th STEP - KNIFE-SWITCHES, GRID SYNCHRONISERS, INVERTERS Let’s assume that the consumer has bought the Wind Turbine. If he has a grid nearby, he will want that he should have small Turbine but during peak consumption the home electric wiring net would “pump” the required failing energy out of grid automatically or manually. For example once a year he uses 10kW electric plough. The rest time he consumes 3 kW in peak. There are several solutions of this task: - The consumer should have a separate (parallel) grid-connected wiring for high-power devices. - The consumer installs the knife-switch on the input of household wiring net. It allows manually turn the switch between Wind Turbine and the grid. The disadvantage of such switching is voltage jump which causes the re-adjustment of some devices (electric clocks, some constantly operating devices). - The consumer buys more powerful inverter, after he has made all necessary calculations. In our case it’s 10kW + 3kW + some reserve (let’s say 1kW) = 14 kW inverter (current price in the store is about 6,000 Euros). Grid wiring (phase, ground) should be connected to special input of inverter. In case of peak loading or windless weather the inverter will automatically start to “pump” the energy out from grid. The variety of this case is the connection to diesel generator. NOTE: The output of inverter with batteries should NOT be connected in parallel with grid as it will explode because of discrepancy of phases, amplitudes and frequencies. Small Wind Turbines (up to 10 kW) are simple in assemblage, montage and servicing. Thus we recommend to install several small Turbines instead of one big. For example instead of WPU-9 (9 kW) it’s better to install three WPU-3 (3 kW) with total power 9 kW. |