Wind Generation

Wind Generation 09/02/11:

Wind generation energy analysis is for the period 7th September to 7th December 2010 and is half hourly data relating to UK Generation by Fuel Type downloaded in Excel format from the internet. During the period of analysis the UK wind turbine metered capacity was 2430MW, it is now 2662MW.

The chart below, generated from the analysis period data illustrates the UK average generation by type within the period.

The chart shows that wind generation only averaged 1.77% over the period.

Looking in more detail at the Excel data it illustrates that the maximum demand on the generators in the UK (MDUK) of 59747MW occurred on the 6th December 2010 at 18:00 and the proportion delivered by wind generation was 291MW (0.49%) or 12% of its metered capacity. Conversely, the minimum demand, which may be incorrect, of 10409MW occurred on 19th October 2010 at 10:30 co-incidental with wind generation of 118MW (1.13%) or 4% of metered capacity.

The best performance figures for wind occurred on the 12th November 2010 at 12:30 when 2065MW (4.68%) ofUK generation or 78% of metered capacity was achieved. Over the three months, wind generation averaged 25% of it’s metered capacity.

There is some contradition between the recorded generation demand, which currently includes 2662MW of wind capacity, for the UK and the claims of Renewable UK. 

Currently operational – at a glance…

Projects

Turbines

Megawatts

Homes Equivalent

CO2 reductions (pa)

SO2 reductions (pa)

NOX reductions (pa)

283

3153

5203.795

2909696

5880497 tonnes

136756 tonnes

41027 tonnes

They claim almost 100% more capacity (5203MW)! How this is interpreted is important because, if they are correct but, the energy trading figures are also correct and one has to assume they are, it would halve the percentage delivery of wind turbines against metered capacity.

Clearly, wind generation only delivers a small proportion of the requirement to delivery 10% of energy through renewable sources by 2010. The question is; what is the 10% based on? Obviously, wind  can’t be guaranteed to substantially support the UK peak demand, therefore the average figures displayed in the chart above must used.

In the 3 month period UK generation (calculated excluding losses) supplied 84 million MWh of electricity equal to 45million tonnesCO2 with 1.4 million MWh from wind power.

Yearly, this would be approximately 337 million MWh or 183 million tonnesCO2, wind delivering 5.7 million MWh.

Summary of UK Generation by Fuel Type 07/09/10 to 07/12/10

Total MW & Ave %

MWh

kgCO2

CCGT

73260608

36630304

19926885376

CCGT%

43.91%

 

 

OIL

86352

43176

23487744

OIL%

0.04%

 

 

COAL 

58045150

29022575

15788280800

COAL%

33.06%

 

 

NUCLEAR

28634570

14317285

7788603040

NUCLEAR%

17.63%

 

 

WIND

2891977

1445989

786617744

WIND%

1.79%

 

 

PS

1515256

757628

412149632

PS%

0.79%

 

 

NPSHYD

1616892

808446

439794624

NPSHYD%

0.97%

 

 

OCGT

17703

8852

4815216

OCGT%

0.01%

 

 

OTHER

0

0

0

OTHER%

0.00%

 

 

INTFR

2676860

1338430

728105920

INTFR%

1.78%

 

 

INTIRL

0

0

0

INTIRL%

0.00%

 

 

INTNED

0

0

0

INTNED%

0.00%

 

 

ENERGY TOTAL (3 months)

168749763

84374881

 

ESTIMATED ENERGY TOTAL (12months)

674999052

337499526

 

 

MW

MWh

 

TonnesCO2 (3 months)

 

45898740

45898740

Estimated Tonnes CO2 (12 months)

 

1835945860

183594960

Green energy Tonnes CO2 (adjustment)

 

 

9427165

Estimated adjusted Tonnes CO2/Annum

 

 

174167795

The table above provides summary data calculated from the 3 months of half hourly data in the Excel file. A green energy tonnesCO2 adjustment has been made which includes, nuclear, wind, pumped storage and non-pumped storage hydro, leaving a final estimated annual CO2 figure for electricity generation of 174 million tonnesCO2. This compares favourably with the www.stela-led.co.uk  website where it is stated that in 2006, CO2 produced by electricity generation was 181 million tonnes. Also, the adjustment shows that the carbon reduction of the combined “green generation” is approximately 5% or a 50% shortfall against the 2010 target. The inclusion of nuclear generation is the major contributor to achieving the 5%!

Based on the conflicting information available it appears that the UK has between 1500 and 3000 operational wind turbines notionally rated between 2MW and 3MW each. Assuming the number is in between say 2500; for the 2010 target of 10% renewable energy >8000 wind turbines would be needed! For the planned additional 7000 turbines to hit the 2020 target of 30% reduction in UK carbon emissions it will be necessary to install 15 wind turbines per week and it is likely this will achieve less than 7% carbon reductions. Projecting to 2050, for the UK to achieve 50% reduction in carbon emissions, it will require 70,000 operational wind turbines. These estimates do not include the potential UK generation demand in 2050. With estimated 20 – 25 year life cycle for wind turbines, by 2050 they will need renewing for the second time. 

The problem is the inconsistency of wind. Generator output is dependant upon the aerodynamic rotor efficiency, which may vary according to wind speed, the swept area of the blades, and the power density of the wind/m³. The example, in the table below, is very simplistic but illustrates the effect of wind variation on turbine output. This demonstrates that if the wind speed drops by 50% the generator output is reduced by 87.5%. In practice this is not strictly correct; the Cpoa efficiency is greater at lower wind speed and mean wind speed has to be factored into the calculation, resulting in improved output. However, it is essential that back up generation is available at short notice to support wind speed variation.

 

Aerodynamic rotor efficiency

PI

Swept area of blade

Swept area of blade

Power density of wind/m³

Wind speed

Wind speed

Wind speed

Generator efficiency

Output GW

Cpoa

R

R

PA

M/S

M/S

M/S

G effic

3.0

0.32

3.14

40

40

0.6125

15

15

15

0.9

0.37

0.32

3.14

40

40

0.6125

7.5

7.5

7.5

0.9

 The future security of electricity supply in the UK will depend upon the surplus generation capacity. In the short term, at the end of January 2011, minimum weekday surplus capacity was 7000MW and maximum weekday surplus was 10000MW. The 12 month, weekly surplus forecast is more optimistic with predictions between 12000MW & 18000MW and even higher between weeks 29 and 35, July/August (20000MW to 23500MW).

However, the future closure and decommissioning of old power stations needs to be considered. The information found and used in this report suggests that the following closures are likely.

    Nuclear between 2015 and 2020: 5220MW

    Coal Fired by 2015: 7901MW

    Oil by 2015: 4323MW

 

A loss of 17444MW of generating capacity; this would seriously compromise the ability of the generators to match the UK electricity demand. But, it also identifies that there are coal (2840MW) and gas (7295MW) power stations proposed or under construction. At 10135MW total, the new plant will help but situations where minimum surplus is down to current levels may be critical.

One has to conclude that for long term security of supply the UK cannot rely upon renewable energy as a significant source of electricity and serious development of coal fired generation, with carbon capture and storage if possible, coupled with nuclear generation to replace the planned decommissioning of old plant should be the way forward. The main argument against nuclear power is the storage of contaminated waste but this is offset by the low carbon emissions.

The analysis of the CO2 produced by electricity generation led to consideration of information available on the internet relating to UK nominal Voltage. Within the Electricians Guide to the 16th Edition IEE Wiring Regulations http://www.tlc-direct.co.uk/Book/1.1.htm the following statement is made. It is supported in more detail on the website of a leading UK supplier and manufacturer of stabilised Voltage optimisers.

~~~~~~~~~~~~~~~~~ 

This Electrician’s Guide

Note on Supply Voltage Level
For many years the supply voltage for single-phase supplies in the UK has been 240V +/- 6%, giving a possible spread of voltage from 226V to 254 V. For three-phase supplies the voltage was 415 V +/- 6%, the spread being from 390 V to 440V. Most continental voltage levels have been 220/380V.

In 1988 an agreement was reached that voltage levels across Europe should be unified at 230V single phase and 400V three-phase with effect from January 1st, 1995. In both cases the tolerance levels have become -6% to +10%, giving a single-phase voltage spread of 216 V to 253 V, with three-phase values between 376V and 440 V. It is proposed that on January 1st, 2003 the tolerance levels will be widened to +/- 10%.

Since the present supply voltages in the UK lie within the acceptable spread of values, Supply Companies are not intending to reduce their voltages in the near future. This is hardly surprising, because such action would immediately reduce the energy used by consumers (and the income of the Companies) by more than 8%.

In view of the fact that there will be no change to the actual voltage applied to installations, it has been decided not to make changes to the calculations in this book. All are based on the 240/415V supply voltages which have applied for many years and will continue so to do.

In due course, it is to be expected that manufacturers will supply appliances rated at 230 V for use in the UK. When they do so, there will be problems. A 230 V linear appliance used on a 240 V supply will take 4.3% more current and will consume almost 9% more energy. A 230 V rated 3 kW immersion heater, for example, will actually provide almost 3.27kw when fed at 240 V. This means that the water will heat a little more quickly and that there is unlikely to be a serious problem other than that the life of the heater may be reduced, the level of reduction being difficult to quantify.

Life reduction is easier to specify in the case of filament lamps. A 230 V rated lamp used at 240 V will achieve only 55% of its rated life (it will fail after about 550 hours instead of the average of 1,000 hours) but will be brighter and will run much hotter, possibly leading to overheating problems in some luminaires. The starting current for large concentrations of discharge lamps will increase dramatically, especially when they are very cold. High pressure sodium and metal halide lamps will show a significant change in colour output when run at higher voltage than their rating, and rechargeable batteries in 230 V rated emergency lighting luminaires will overheat and suffer drastic life reductions when fed at 240V

There could be electrical installation problems here for the future!

~~~~~~~~~~~~~~~~~

Basically, the above document states that, although the voltage levels were unified in 1995, the distribution transformer tappings were not altered. The following example based on load impedance of 10 Ohms shows the impact of transformer tap down on the active energy demand.

Volts V

Impedance Ω

Amps I

Watts

 

240

10

24

5760

 

230

10

23

5290

 

 

 

 

9.2%

Energy Saving

It is reasonable to suppose that if this is still the case then, because there is 0.544kgCO2/1kWhe, a 5% transformer tap down of the UK distribution network would not only bring supplies in line with nominal Voltage but, reduce the UK electricity generation CO2 produced by a similar amount equal to 16 million tonnesCO2/Annum. Obviously, there may be some cases where installations with significant Voltage drop may experience some problems with motors and discharge lighting but, on the whole modern electrical equipment is designed to operate at 230/400V nominal and onsite Voltage recordings often exceed this.

This action would not require the purchase or installation of any equipment just a manual process at each distribution transformer. The benefits are twofold the UK tonnesCO2 from electrical generation is dramatically reduced and the customers reduced electricity consumption lowers their KWh and CCL charges. This would result in lower energy and generation demand.   

   

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