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Aloha to all, let me introduce myself. I was scheduled to speak on February 27th, 2010, and as luck would have it – a Tsunami Warning came about…and thus our workshop was cancelled. I promised my daughters an adventure on the Big Island, and an adventure they got! The island was thankfully spared, the earth was quieted, and many of us have gotten back to wondering about wind energy, specifically residential or “small” wind.
My presentation was intended to provide some general technical and economics background about the installation of residential wind turbines, with special consideration to the conditions on this Big Island, and to the potential benefits to its residents.
Background -- Hawaii State has introduced bills in 2010 to accelerate Hawai‘i’s progress in reaching the goal of 70 percent clean, renewable energy by the year 2030. The hope for the long term is to not only stabilize and reduce the cost of electricity compared to the cost of electricity from fossil fuels, but also to
constructed single-family residences after January 1, 2015, such that on-site generation of power can cover the balance of the power needed to operate the home (Net Zero Energy Construction HB2521 / SB2674). Under the Public Utility Regulatory Policies Act (PURPA) of 1978, utilities are required to allow customers with renewable electricity generators, powered by wind, solar and others, to interconnect their systems to the grid (Am.Wind Assoc. Windletter, July 2006).
Wind electricity is produced from the kinetic energy of the wind, which causes the wind mill blades to turn and to drive a generator, and is converted by an inverter from DC to AC to either 1) provide power directly to the home, or 2) charge a battery, or 3) if not all of the power produced from the Small Wind turbine is needed, fed into the grid. The system diagram on the WindEnergy website illustrates this as a Net Zero Construction system (without grid connection), together with synergistic solar photovoltaic (PV) panels.
Unfortunately, wind power is intermittent and not in synch with electric energy demand. Utilities therefore need to resort to energy management schemes (such as interruptible service, energy storage (such as batteries, pumped hydro or hydrogen) and stand by generators. … while continuing to provide power at a voltage and frequency that deviate little from set norms, despite having to add such renewable but non-constant supplies of energy to the grid.
Households in Hawaii are fortunate for averaging monthly electricity consumption of only about 200 kWh, whereas average mainlander consumption ranges from 500 to 950 kWh, for a family of four people and an 1800 sq. ft. home. The bad news is that for residents in Hawaii County, the electricity rates now average 0.4088 $ / kWh, with all fees and energy cost factors included, and is the highest in the nation. But such high rates are also an inducement to install residential wind or solar generators.
But before we size and put up residential wind turbines, let us talk about your energy consumption. It is imperative that first perform a set of common-sense energy conservation tasks. The first step to savings is to identify where your energy is being used. Once you know this, then you can take steps to reduce energy consumption. Working with Energy Star appliances, solar water heaters, changing your incandescent light bulbs to CFL’s, using low-flow faucets and showerheads, using low-water-use washers and dishwashers, and checking for water leaks are some of the common things that you can do for energy conservation and efficiency in your homes.
Technology -- Then lets get to my preferred topic: How to bring renewable wind energy into your home. The size of a residential wind turbine depends on the available wind speeds and the local capacity factor. Wind speed maps are available from AWEA or AWS Truewind. You can find one for the Big Island if you go to www.heco.com. These wind maps, however, only show you capacity wind areas from 20 mph winds and higher based on 50 or more meters high (approx. 160 ft). This pertains to siting of Big Wind turbines and only approximately to Small Wind turbines.
Small Wind turbines will need to meet certain topographical and wind criteria. Open areas to the prevailing winds (on the island – NE, NW, and S); if not totally open, turbine head should be 15 to 20 feet above the obstacles (buildings, trees) or the pole sited at least 450 feet away from them and within 200 feet of your home. The pole may have to be farther away depending on the height of your trees; and the availability of average wind speeds at 12 mph the majority of the year. With regard to wind, your elevation, terrain, season, and relationship to the mountains, as well as esthetics in the eyes of your neighbors, are essential parts of deciding whether your location is suitable for a wind generator.
In the north at Kapaau and nearby, homeowners are getting over and above the rated performance of their wind turbines (over 850 kWh a month). In my own installation experience of 34 units in NE Pennsylvania, we generate anywhere from 20 to 65% of our own power from our wind turbines, but we consume the above-mentioned average of 950 kWh. Hawaii has far lower average energy consumption and far greater wind capacity factors than Pennsylvania. Wind speeds are variable in all areas. To measure and quantify available wind speeds, the use of anemometers are fine, but their accuracy drops when the wind is predominantly gusty. Some wind turbines, they will automatically shut themselves down in gusty wind. This emergency brake saves their mechanical parts from over-working and protects the lifetime of the unit. These smart turbines will then turn themselves back on when they find the wind is smooth.
Economics – Thanks to the “Green Energy ROI and Electricity Cost Calculator” now available on this website, we can go through one example calculation, based on the inputs listed below and provided by U.Bonne. The listed tax credits are estimated and need to be confirmed. It computes annually-compounded, average ROI (over the life of the equipment), monthly utility bill savings (allowing for the minimum utility bill), and cost of the generated electricity, among other parameters. For a typical “Small Wind” Skystream 3.7m, 2.4 kW(peak) Wind Turbine system we get:
Calculator Inputs
Peak generator output 2.4 kW (AC)
Capacity factor 30 %
Generator product life 10 years (lim. warranty: 5 years)
Loan Interest 4.0 %/year
Fuel-based electricity cost 0.4077 $/kWh
Capital investment 19,500 $ (incl. post and inverter)
Fed tax credit/refund 20 % of capital investment
State tax credit/refund 10 % of capital investment
Crude oil cost 80 $/barrel
Monthly minimum utility bill 22.16 $/month
Calculator Outputs
Life cumulative minimum utility bill 2,659.20 $
Capital investment after subsidies 14,040.00 $
Electric energy savings 6,307 kWh/y
Electric energy cost savings 2,305.53 $/year
Crude oil import savings 1,547.60 $/year
Return on assets 16.42 %/year
Payback time 7.12 years
Mortgage payments (minus util.bill) 2,305.53 $/year
Compound AAROI 4.73 %/year
Total generator life ROI 47.3 %
Normalized cost of system 5.85 $/W (peak)
Normalized cost of system 19.50 $/W (avg)
Averaged output electricity cost 0.302 $/kWh
As shown, and despite the low (but still higher than present bank savings account earnings) annualized and averaged ROI of 4.73%/year, the cost of the wind-produced electricity of 0.302 $/kWh is lower than the present price of 0.4077 $/kWh for the Big Island, despite the conservative inputs, and does not negate the business merit of installing such a wind mill system. Wind mill system costs are coming down, just as solar PV systems are. If the system cost came down to $17,000, electricity cost would drop to 0.265 $/kWh and the AAROI increase to 7.37 %/year. If the energy produced were to also cover the monetary value of the Minimum Charge utility bill, the AAROI would increase to 9.69 %/year. The readers are invited to examine the effect of changing other variables, and even enter values corresponding to solar PV systems.
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* Sandra Babuka is a Specialist Director of Renewable Energy for Trehab Agency, Mainland – Pennsylvania; Certified Small Wind Turbine Installer and Energy Conservation www.trehabrenewableenergy.com; , M.A. Education, Environmental Science and Education Instructor, Axia University and Salt Springs State Park; Board of Directors - Friends of Salt Springs State Parkwww.friendsofsaltspringspark.org; Previous President of ReS.C.U.E. (Return Susquehanna County Under Ecology) – Active member www.rescue-nepa.org ; Previous Board of Ecologia - (ECOlogists Linked for Organizing Grassroots Initiatives and Action) was founded by grassroots environmental activists from the United States, in 1989, in order to support grassroots environmental initiatives across the Soviet Union and eastern Europe www.ecologia.org
Edited by Ulrich Bonne |
