ONE: ENergy Needs
Sizing a wind system is highly dependent on the energy requirements that your household has. That is why it is very important to calculate how much energy you need to generate with your Weaver wind system!
If your household is off-the grid, start by listing the electrical loads you wish to power, as well as the quantites per load. It is also important to obtain the wattage per appliance (power required to operate it), which may usually be found in the equipment's label.
- Lamps 10 unit x 8 Watts per Unit = 80 Watts Total
- Television 2 unit x 120 Watts per Unit = 240 Watts Total
- Computer 1 unit x 80 Watts per Unit = 80 Watts Total
- Fridge 1 unit x 180 Watts per Unit = 180 Watts Total
Once you know the wattage per load type, estimate how many daily hours will you be using each particular load (for a fridge usually 8 hours are considered, which is the average daily time the compressors is consuming energy).
The energy demand per load (in Watt-Hours) may be calculated by multiplying the power per load type with the average daily running time.
- Lamps 80 Watts x 8 hours/day = 640 Watt-Hours/day
- Television 240 Watts x 4 hours/day = 960 Watt-Hours/day
- Computer 80 Watts x 6 hours/day = 480 Watt-Hours/day
- Fridge 180 Watts x 8 hours/day = 1440 Watt-Hous/day
Finally, add up all the energy requirements to get the daily energy needed for your household! For the example, it adds up to 3520 Watt-Hours/day, or 3.52 kWh/day.
If your household is connected to the grid, the primary function of your wind system will not be powering your loads directly, but reducing the energy consumed from the grid by self-generating a fraction of the power your hosehold demands. You may find your average energy demand in your energy bill, since utilities charge you based on your monthly energy use in kilowatt-hours (kWh).
TWO: Know Your Site
When doing a preliminary site survey, keep an eye out for three things: first, find a suitable location for your turbine. Try to keep it as close as possible to your household (so wiring distance is minimized), but not so close that the noise of the spinning blades or the shadow cast by the turbine would become a nuisance.
Seconds: when choosing the turbine location, also try to steer clear of tall obstacles (buildings or trees) that interrupt the incident wind flow towards the rotor.
Finally, try to get some information regarding the availability of the wind resource in your area. The National Oceanic and Atmospheric Administration (NOAA) website has a comprehensive database of weather data from weather stations distributed across the United States, from which you may find the average annual wind speed in your area.
You may also get a gross estimate of the average wind speed in your location from the linked map (made by the National Renewable Energy laboratory (NREL) and AWS Truepower).
THREE: Pick A Turbine
Once you know how much energy your household requires, you are ready to select the Weaver wind turbine that closely satisfies your energy requirements.
Accurately predicting the annual energy yield of a wind turbine is a complex process that involves site measurements, statistical analysis, application of probability functions and detailed knowledge of the turbine's power curve. Fortunately, there is a simple formula that gives a gross estimate of the annual yield from a particular turbine:
Annual Yield (kWh/year)= 0.01328 * D (ft) ^2 * V (mph) ^3
To estimate the annual yield of turbine, multiply the given constant with the square of the rotor diameter in feet, and then by the average annual wind speed at the site in mph cubed.
For example, for a site with a mean annual wind speed of 4 meters per second (8.92 mph), a Weaver 5 turbine (rotor diameter of 4.98 m, or 16.3 ft) would generate:
0.01328 * (16.3ft)^2 * (8.92mph)^3 = 2504.2 kWh/year, approximately 6.86 kWh/day
As a rule of thumb, choose a Weaver turbine that generates around 20-30% more daily energy than the calculated daily demand for off-grid locations from step one.
For grid-tie locations, the ratio between turbine yield and your daily energy demand determines the percentage of energy self-generated by the system (that is, energy you will avoid consuming from the grid). If the ratio is larger than 1, it means that you may sell excess power to the grid with the Weaver turbine chosen.
Four: CHoose a Tower
We offer three different tower options to support our turbines: Guyed, Self-Supporting and Monopole. All of them are designed and built to safely support Weaver wind turbines in harsh weather conditions.
Choosing a tower is a matter of personal preference, mainly concerning aesthetics and budget. The guyed tower is our cheapest option, but it has the largest footprint and the wiring involved can be cumbersome for some. The self-supported tower has a much smaller footprint, but is also heavier, has a more "massive" look and requires more maintenance. Finally, the monopole has the smallest footprint, arguably is the best looking of the three, but is also the most expensive.
FIVE: PICK THE INVERTER
The inverter is a central component in wind and solar photovoltaic systems, since it is the device that conditions the energy produced by the turbine or array, in order for it to be able to power your loads.
We offer three inverter choices: the GT-2 (2kW), the GT-5 (5kW) and the PPS-10 (10kW).
If your system is for off-grid use, or if you wish to have energy storage, only the PPS-10 inverter is suitable for the application, no matter which turbine you chose.
For grid-tie systems, we recommend the following inverter configuration:
- Weaver 2 GT-2 Inverter 1 Unit
- Weaver 5 GT-5 Inverter 1 Unit
- Weaver 15 GT-5 Inverter 3 Units
SIX: ENERGY STORAGE
The final step is choosing an energy storage solution, should you require any. As stated before, there are two reasons why you might want energy storage: (1) the system is designed to be 100% off-grid, or (2) you might want to store energy produced when the turbin'es production excedes energy demand, and then use that energy when the situation is reversed.
For Off-Grid solutions, sizing the appropiate storage solution is simple: begin by taking the daily energy demand calutated in step two (3520 Wh/day for our current example), multiply by the desired number of days of autonomy and then divide by the maximum percent discharge that the batteries should be allowed to have to obtain the required capacity in Watt-hours. For our example (considering 1.5 days of autonomy):
Storage Capacity (Wh)= 3520 Wh/day x 1.5 days / 0.8 = 6600 Wh/day= 6.6 kWh/day
Weaver Wind offers Lithium-Ion storage options exclusively. Li-Ion batteries are more expensive tan "conventional" storage technologies such as Lead-acid or gel batteries, but they are also longer-lasting and may be discharged deeply without generating significant damage to the system. Thus, an 80% maximum discharge is the default we recommend for the calculation.
We offer four different storage solutions: 7.7, 15.4, 23 and 38.4 kWh sizes. Just round up the calculated number to the nearest storage solution and you're done! For the example, our 6.6 kWh/day storage needs would be nicely covered with the 7.7 kWh solution.
For grid-tie solutions and other applications that require storage, please contact us as we would be glad to help you size your system.