Daniel at Work

A blog about Small Wind Energy

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Sizing a Battery Bank - Part 1

The easiest way to size a battery bank is to begin by calculating how much electricity you use in a day. Because electrical consumption varies from month to month, your best bet is to determine monthly consumption and then determine the daily rate during the month of greatest consumption.

Once you determine how many killowatt-hours of electricity you will consume per day during your most energy-intensive month, you must make an educated guess as to the number of windless days that occur in that time. That's how long your renewable energy system will be sidelined by a lack of wind.

In most cases, renewable energy designers plan for three days of no wind. Battery banks are then sized to meet one's electrical needs for three days. Longer reserve periods - five days or more - may be required in some areas.

Note: backup fossil-fuel generators are often included in off-grid systems, since they can reduce the need for a large battery bank.

Let's now look at an example to see how this works. Let's suppose that you, your business or your farm consume four kilowatt-hours (4,000 watt-hours) of electricity a day on average during the most energy-intensive month. If you need five days of battery backup, you will need 20 kilowatt-hours of storage capacity (5 days x 4 kilowatt-hours).

by Daniel Coelho

Marketing and Sales Manager at SILENTWIND

E-mail: [email protected]  

Website: www.silentwindgenerator.com  

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Choosing Batteries Part 2 - Sealed Batteries

Currently, two types of sealed batteries are available: absorbed glass mat (AGM) batteries and gell cell batteries. 

Also known as captive electrolyte batteries, sealed batteries lack filler caps. They are filled with electrolyte at the factory, charged, and then permanebtly sealed. Because of this, they are easy to handle and ship without fear of spillage. They won't even leak if the battery casing is cracked open, and they can be installed in any orientation - even on their sides.

Sealed batteries are often referred as "maintenance free" because fluid levels never need to be checked and because the batteries never need to be filled with water.

Eliminating routine maintenance saves a lot of time and energy. It makes sealed batteries a good choice for off-grid systems in remote locations where routine maintenance is problematic (e.g. rarely occupied cabins or remote cottages). Sealed batteries are also used on sailboats and RV's where the rocking motion would spill the sulfuric acid of flooded lead-acid batteries.

Advantages over lead-acid batteries:

they charge faster

they don't release explosive gases

much more tolerant of low temperatures

they discharge more slowly when not in use

Disadvantages:

much more expensive

they store less electricity

shorter lifespan

they can't be rejuvenated if left in a state of deep discharge for extended periods

by Daniel Coelho

Marketing and Sales Manager at SILENTWIND

E-mail: [email protected]  

Website: www.silentwindgenerator.com  

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Choosing Batteries Part 1 - Off-Grid Systems

Wondering about the best batteries for your wind or hybrid wind/solar system? For off-grid systems, your best choice is a deep-cycle flooded lead-acid battery like those made by Trojan, Rolls, Deka and others.

Renewable energy systems require deep-discharged lead-acid batteries with thick lead plates. The thickness of the lead plates allows them to withstand multiple deep discharges - so long as they're recharged soon afterwards. Even though the plates loose lead over time, they are so thick that the small losses are insignificant. As a result, a deep-cycle battery can be deeply discharged hundreds, sometimes a few thousand times, over its lifetime.

Deep-cycle flooded lead-acid batteries that are promptly recharged after deep discharging, routinely equalized, and housed in a warm location, could last for up to ten years, maybe even longer.

by Daniel Coelho

Marketing and Sales Manager at SILENTWIND

E-mail: [email protected]  

Website: www.silentwindgenerator.com  

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Neodymium Magnets: Why Choose Them?

Alternators in many small wind turbines contain rare earth magnets, rather than electromagnets which are found in the alternators of cars and trucks.

(An electromagnet creates a magnetic field by running an electric current through copper wire coils or windings). Rare earth magnets contain neodymium, iron and baron. They produce a much stronger magnetic field than conventional iron (ferrite) or ceramic magnets used in many small wind turbines. The stronger the magnetic field, the greater the output of a wind generator, all things being equal.

Generators that use magnets like rare earth magnets, as opposed to electromagnets, are referred to as permanent magnetic generators. The magnets are mounted on a rotor of the generator (the part that spins).

by Daniel Coelho

Marketing and Sales Manager at SILENTWIND

E-mail: [email protected]  

Website: www.silentwindgenerator.com  

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Calculating Return on Investment of a Wind System

ROI can be calculated by dividing the annual value of electricity generated by a wind system by the cost of the system

As a simple example, suppose a wind energy system produces $1,000 worth of electricity each year and costs $10,000 to install. The simple return on investment is $1,000 divided by $10,000, or 10 percent.

However, simple return on investment does not take into account a number of economic factors that could influence one's decision. For instance, it does not include interest payments or loans required to purchase the system or lost interest if the turbine and tower are paid in cash. It does not take into account insurance costs or property taxes. All of these factors decrease the value of the investment.

This calculation also does not take into account factors that increase the value of this investment, for example, the potential increase in the cost of electricity from the local utility. This would make wind generated electricity more valuable.

by Daniel Coelho

Marketing and Sales Manager at SILENTWIND

E-mail: [email protected] 

Website: www.silentwindgenerator.com  

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Economic Performance of a Wind Energy System

One can analize if it makes economic sense to install a wind energy system by comparing the cost of electricity of the wind system with the cost of electricity from the local utility. 

First, you must determine the average monthly consumption of your house. Second, determine the average monthly wind speeds at the site. Third, identify a wind turbine that meets your needs.

After estimating the monthly electrical production, convert this to annual electrical output. A 1KW turbine could produce up to 225 kw/h per month (at 13 miles/hour) or 2.700 kw/h per year. Now multiply the kw/h produced in one year by the life of the system.

Wait a minute! The life of the system? How long would that be? Well, it depends. A good quality turbine could last 20 years with good maintenance; a cheaper model only 5 or so. If we consider a 15 years life time for the 1KW turbine, it would produce 40.500 kw/h over its lifetime.  

Let's also consider a cost of $6.000 for the wind system (turbine + mast + batteries + installation). Dividing the cost of the system by the total output yields the cost of electricity per kw. In this example, the electricity generated by the turbine will cost about 15 cents per kw/h. 

This system would make economic sense if you were paying 15 cents or more per kw to the local utility. Just don't forget that you have to prepay your electrical bill, laying down $6.000 all at once.

by Daniel Coelho

Marketing and Sales Manager at SILENTWIND

E-mail: [email protected] 

Website: www.silentwindgenerator.com  

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Energy Demand in Your New Home (Part 2)

Energy consumption can be more accurately determined by consulting the product labels of appliances and electronic devices. The information available usually consists of power consumption in watts and perhaps amperage and voltage.

If the labels only display amperage and voltage, you can determine watt consumption by multiplying the two. Watts = amps x volts. 

One can also determine wattage by the use of a meter. They are plugged into electrical outlets, and appliances you want to monitor are plugged into them via a receptacle on the meter. The display on the meter shows wattage consumption of the device.

by Daniel Coelho

Marketing and Sales Coordinator at SILENTWIND

E-mail: [email protected]

Website: www.silentwindgenerator.com 

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Energy Demand in Your New Home (Part 1)

Before choosing (and installing) a small wind turbine, you will want to calculate your future consumption of energy.

Energy consumption in a new home can be determined in a number of ways. One way is to base your future consumption on the consumption in your actual home. This could not work thow, if you are planning to build a more efficient home (energy-efficient lighting or appliances).

One other way is to use a load analysis. For this you can use a worksheet where you will list all the appliances and lights you expect to install. Afterwords determine how much electricity each one uses and the number of hours per day they will be operating. This exercise can give you an estimate for energy demand.

For energy consumption of various electrical devices, you can seek for charts available in books and online. See below an example.

by Daniel Coelho

Marketing and Sales Coordinator at SILENTWIND

E-mail: [email protected]

Website: www.silentwindgenerator.com 

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Charge Control in Battery Based Systems

A component found in wind energy systems, either off-grid or on-grid with battery backup is the charge controller. When the charge controller sees that the batteries are fully charged, reaching the full voltage set point, it terminates the flow of electricity to them. This is normally done in one of two  possible ways: dump load or electronic brake of the rotor.

Dump load: the charge controller divertes surplus electricity to a dump load, a resistance that turns electricity into heat.

Electronic brake: the charge controller brakes the spinning of the rotor, through a soft short circuit, in order to stop energy production by the wind turbine. 

by Daniel Coelho

Marketing and Sales Coordinator at SILENTWIND

E-mail: [email protected]

Website: www.silentwindgenerator.com 

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Wind Turbine Swept Area

In theory, a ten percent increase in swept area will result in a ten percent increase in electrical production. Doubling the swept area doubles the output. 

When searching for a wind turbine, you can calculate the swept area using the equation A = Pi . r2, where A is the circle of the area. Pi is a constant of 3,14 and r is the radius of the circle (the same as the blade lenght).

by Daniel Coelho

Marketing and Sales Coordinator at SILENTWIND

06/5/13

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Smart Sitting For Small Wind Turbines

Home applications: To avoid costly mistakes, make sure your wind turbine is mounted so that the complete rotor (hub and blades) of the wind generator is at least 30 feet (9 meters) above the closest obstacle within 500 feet (about 150 meters), or a tree line in the area, wichever is higher. This should place the turbine out of the turbulence bubble into the stronger, smooth-flowing winds.

by Daniel Coelho

Marketing and Sales Coordinator at SILENTWIND

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Galeria de Daniel T Coelho no Flickr.

Silentwind turbine photo collection 2010-2013 all around the world.