Renewables: April 2009 Archives

I have recently measured wind speed in my back garden for 1 year from April 23rd 2008 to April 23rd 2009 at 4 m. We live in Upperchurch in Co. Tipperary and the area would be considerd by locals and visitors a windy place all year round, and bleak spot in the winter.

I then applied a scaling factor of 0.61 (i.e. divide the reading by 0.61) to bring the wind speed up to 10 m height this figure was based on data provided by http://www.sustainability.ie/microwind.html and had a higher shear factor than RETscreen recommended i.e. I was generous in my estimation.

Accorrding to the wind maps the wind speeds for Upperchurch are 6 - 6.25 m/s at 50 meters. At 10 meters my average measured wind speed was 3.83 ms (this is upscaled) the measurement at 4 meters was 2.3363 m/s .

Number of hours for each wind speed were as follows.

April 23 2008 - April 23 2009 extimated wind speed at 10 meters height
m/s	Hours
0	1261.833
1	747.4167
2	890.8333
3	1443.333
4	1395
5	1040.583
6	393.4167
7	597.5833
8	390.75
9	243.9167
10	84.91667
11	110.9167
12	75.16667
13	40.91667
14	23.25
15	20.16667

Using Mike Sagrillos Wind Swept Area Calculations I generated a payback table based on wind turbine diameter only I calculated the income that would be generated from selling back to the grid. The first 3,000 KW hrs are priced at 19 cents and the remainder at 9 cents.

The results are as follows:

Diameter (meters)	Turbine Output at 10m/s	Kw Hrs	Income
2	0.77	1159	220
2.2	0.93	1402	266
2.4	1.1	1669	317
2.6	1.3	1958	372
2.8	1.5	2271	431
3	1.7	2608	495
3.2	1.96	2967	563
3.4	2.2	3349	601
3.6	2.48	3755	638
3.8	2.78	4184	676
4	3	4636	717
4.2	3.4	5111	760
4.4	3.38	5111	804
4.6	4	6131	851
4.8	4.4	6676	900
5	4.8	7244	952
5.2	5.18	7835	1005
5.4	5.59	8450	1060
5.6	6.02	9087	1117
5.8	6.45	9784	1177
6	6.9	10432	1238

These figures should help you to estimate the payback time. Look up the turbine's diameter and look across to the income.

A breakdown for a 3 meter radius turbine is provided below

3 meter radius turbine
Rotor M	Rotor feet	m/s	mph	Power (kW)	Hrs	Energy (kWh)
3	10	3	6.75	0.046624	1443.333	67.29332
3	10	4	9	0.110515	1395	154.1685
3	10	5	11.25	0.21585	1040.583	224.6096
3	10	6	13.5	0.372988	393.4167	146.7398
3	10	7	15.75	0.592292	597.5833	353.9436
3	10	8	18	0.884121	390.75	345.4701
3	10	9	20.25	1.258836	243.9167	307.051
3	10	10	22.5	1.726798	84.91667	146.6339
3	10	11	24.75	2.298368	110.9167	254.9273
3	10	12	27	2.983907	75.16667	224.2903
3	10	13	29.25	3.793775	40.91667	155.2286
3	10	14	31.5	4.738334	23.25	110.1663
3	10	15	33.75	5.827943	20.16667	117.5302
					Total Kw	2608.053
					Income	495.53

Urban wind have some very interesting documents on European urban wind turbine manufacturers and an explanation of the terminology


http://www.urbanwind.net/downloads.html


A list of European urban wind turbine manufacturers http://www.urbanwind.net/pdf/CATALOGUE_V2.pdf

Urban Wind Turbine technology review, which has a good explanation of noise from turbines
http://www.urbanwind.net/pdf/technological_analysis.pdf

A renewable energy colleague of mine in Tipperary Institute pointed me towards this excellent document created by the British Wind Energy Association. The standard recommends measuring at 11 m/s, I would prefer to measure at 10 but I cannot argue with the rest of the excellent research.

This standard was created by the small wind turbine industry, scientists, state officials, and consumers to provide consumers with realistic and comparable performance ratings and an assurance the small wind turbine products certified to this standard have been engineered to meet carefully considered standards for safety and operation.

The goal of the standard is to provide consumers with a measure of confidence in the quality of small wind turbine products meeting this standard and an improved basis for comparing the performance of competing products

This performance and safety standard provides a method for evaluation of wind turbine systems in terms of safety, reliability, power performance, and acoustic characteristics.

http://www.bwea.com/pdf/small/BWEA_SWT_Standard_Feb2008.pdf

This standard for small wind turbines is derived largely from existing international wind turbine standards developed under the auspices of the International Electrotechnical Commission (IEC).

Specific departures from the IEC standards are provided to account for technical differences between large and small wind turbines, to streamline their use, and to present their results in a more consumer-friendly manner.

The equivalent BS (British Standard) are quoted for ease of use.

http://www.bwea.com/pdf/small/BWEA_SWT_Standard_Feb2008.pdf

Making an investment in a wind turbine can involve a significant outlaw of hard earned cash. Recent;y on boards.ie someone asked the question why the prices varied so much and what features you should you be looking out for.

In replying to the quesiton I realised that these features should be recorded on my web site. The following is a copy of the answer I posted.

I can't really explain why turbines are prices are so varied. My gut feeling is that it is a combination of several factors.

• Like any business some products have the brand name/reputation priced into the product.
• The components and the quality of build i.e. the heavier and more rugged the turbine the bigger the price.
• Research and Development costs have to be recouped.
• Sales Commission (as pointed out by bladespin on boards.ie)
  
• Warranties on blades and components etc e.g. I paid a slight bit more for solar panels that had a 10 yr warranty

I would try and be objective in the comparison. I would use the following features to guide me.

1- Diameter of blades. Bigger the diameter, the larger the wind swept area.
2 - Weight of turbine
3 - Design of turbine does it cut out at high speeds or does it continue operation.
4 - At what speed m/s was it rated at 2.5 kw.A turbine rated at 12 m/s is different to a turbine rated at 9 or 10 m/s. If turbine A is rated at 13 m/s and turbine B is rated at 9 m/s, turbine A will generate less power at 6 m/s than turbine B.
5 - A what speed does the inverter kick in and generate power i.e. does it generate power at low wind speeds?
6 - Estimated output at 3,4,5,6,7,8,9 m/s. The majority of wind at my house would fall in the 3 - 6 m/s range.
7 - Price of turbine, tower, inverter, installation and grid tie cost
8 - Warranties on blades, tower etc. Remember your turbine needs to be operational for at least 15 - 20 years.
9 - Type of tower tied or monopole
10 - How do you raise lower the tower, hydruallic/crane etc
11 - Service cost per year (approx)
12 - Customer support, is there some one who can get to your site next day to address an issue.
13 - Do you need to oil/grease the turbine on an annual basis.
14 - Do they have any data on noise

Before you buy you should go and see them in operation, and talk to the owners.

The true acid test for any turbine is to record your wind speeds for 1 year and use wind swept area calculations (which uses the diameter) to calculate the number of kw hrs the turbine would generate in 1 year. This will give you a good idea on estimated pay back period.

At the moment I would sooner buy an affordable 2.5 kw turbine than an expensive 6 kw turbine as I feel they blend better in urban/rural areas and offer a realistic pay back period. Smaller blades also mean that the bottom of the blade has a better probability of being taller than the nearest obstacle

Original post http://www.boards.ie/vbulletin/showthread.php?p=59642979#post59642979.