Solar Energy Opportunities

N.K. Tovey (杜伟贤 ) M.A, PhD, CEng, MICE, CEnv

1

CLA Renewable Energy Seminar1st March 2011

• Solar Thermal

• Solar Photovoltaic

• The performance of these technologies

• The challenges of integrating solar energy into

buildings to make most effective use of the resource.

• Life Cycle Issues

1

Recipient of James Watt Gold Medal for Energy Conservation

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• A Partnership between– Broadland District Council– University of East Anglia

• Launched by publicity with an open meeting attended by ~120

• Aims– To promote Solar Water Heating by a community to

enable bulk discounts• Required a minimum of 50 participants to sign up

within 3 weeks• Over subscribed in 22 minutes!• Subsequently 9 properties not found to be suitable

– To develop skills for installing Solar Hot Water Heaters in the region

Technical Opportunities: Solar Thermal:

The Broadsol Project

Solar Collectors installed 27th January 2004

Annual solar collection 750-910 kWh/annum

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Solar Thermal: The Broadsol Project

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Solar Gain (kWh/day)

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1 11 21 31 10 20 1 11 21 31 10 2030 10 20 30 9 19 29 9 19 29 8 18 28 7 1727 7 17 27 6 16 26 6 16 26 5 15 25 4 14 24 6 16 26 5 15 25 5

Sol

ar G

ain

(k

Wh

)

January February MarchApril May JuneJuly August SeptemberOctober November December

20092008

Technical Solutions: Solar Thermal Energy: Performance

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Technical Solutions: Solar Thermal Energy

0.0

1.0

2.0

3.0

4.0

5.0

F M A M J J A S O N D J F M A M J JMonth

kWh/

day

BSD1 BS01BS02 BS12BS14 BS16BS17 BS26BS27 BS29BS52

Up to 15 installations were monitored at 5 minute intervals for periods up to 15 months

Mean Monthly Solar gain for 11 systems

Some 2 panel systems captured twice the energy in summer months as other 2 panel systems.

3 panel systems

The Broadsol Project

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r

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g

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r

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Dai

ly S

olar

Gai

n (

kW

h)

2 Panels

3 Panels

• Three panel systems captured only 13% more energy compared to two panel systems

• Effective use is not being made of surplus in summer6

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jan mar may jul sep nov jan mar may

Syst

em E

ffic

ienc

y(%

)

bsd1

bs01

bs02

bs17

bs26

bs16

bs27

bs52

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30

35

jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun

Syst

em E

ffic

ienc

y (%

)

bs12

bs14

bs29

Measured Overall System Efficiencies – including storage

System Efficiency of 2 panel systems is generally higher than 3 panel systems

2 panel

3 panel

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88

0

20

40

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

kW

h/m

2 /m

onth

Month

0 - Horizontal

45o

90o - Vertical

Tilt Angle variations are not significant in region 0 – 45o

in summer

In winter optimum angles are between 45o and 90o

Optimum orientation in East Anglia is SSW

South West is almost as good as South

Solar Thermal: Performance of Panels

99

More Solar Energy is Collected when Hot Water use is greater.

Sky became hazy at ~ 11:00Substantial hot water demand at 13:30Normal heat loss from tank if there had been no demand shown in black1.157 kWh extra heat collected.Note: further demand at 18:30 leading to further solar collection. Even more solar collection would have been possible had collector been

orientated SW rather than S

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00 03 06 09 12 15 18 21 24Time of Day

Tem

per

atu

re

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En

erg

y p

rod

uce

d e

ach

min

ute

(W

h)

energy

Extra Energy

collector

store

cooling

BS27: 15/05/2004

1.164kWh0.911kWh

1.157kWh

0.083kWh

Technical Issues requiring awareness raising:

• Tank with small residual hot water at top of tank in early morning

• If Central Heating boiler heats up water – less opportunity for solar heating.

Zone heated by solar energy

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Solar Thermal Energy captured when combined with central heating

Tank with small residual hot water at top of tank in early morning

No hot water provided by central heating boiler.

Gain from solar energy is much higher.

More solar energy can be gained if boiler operation is delayed.

Boiler ON/OFF times should be adjusted between summer and winter for optimum performance

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Technical Issues requiring awareness raising:

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The Broadsol Project: Store Temperature Variations

Education of how to get best out of solar HW systems is needed.

Need to adjust timing of central heating boiler over late Spring, Summer and early autumn.

• On day 1, if boiler supplied hot water before solar gain was sufficient, top of tank would be heated to 55o C and reduce the potential solar gain by ~21%.

• On day 2, the loss would be negligible as temperature at top was already over 55oC.

• If the store temperature throughout was as low as 20oC having been drawn off for a bath late on previous evening the loss in potential solar energy gained for having early operation of the boiler can approach 40%.

Day 1 Day 2

The last Government announced a Renewable Heat incentive which would be beneficial for Solar Thermal Installations and provide a financial incentive.

Thus small scale (<20kW) solar thermal would potentially benefit owner by 18 p per kWh and last for 20 years.

In the Comprehensive Spending Review the Government indicated it is still committed to such an incentive and is due to bring forward its plans within the next month.

Solar Thermal: The Renewable Heat Incentive

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Technical Solutions: Solar PhotoVoltaic

Zuckermann Institute for Connective Environmental Research. (ZICER)

Low Energy Building of the Year 2005. Has heat demand ~ 20% of building of its size: 34 kW of Solar Photovoltaic on roof and facade

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Solar Rosette Diagram for East Norfolk/Suffolk

0 30 60 90 120 150 180 210 240 270 300 330 360 N NE E SE S SW W NW N

Azimuth

<20  

20-30  

30-40  

40-50  

50-60  

60-70  

70-80  

80-90  

90-100  

100  

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• Mono-crystalline PV on roof ~ 27 kW in 10 arrays

• Poly- crystalline on façade ~ 6.7 kW in 3 arrays

ZICER Building

Photo shows only part of top

Floor

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• Peak Cell efficiency is ~ 9.5%.

• Average efficiency over year is 7.5%

Mono-crystalline Cell Efficiency Poly-crystalline Cell Efficiency

Actual Efficiency of PV Cells

• Peak Cell efficiency is ~ 14+% and close to standard test bed efficiency.

• Most projections of performance use this efficiency

• Average efficiency over year is 11.1%

Inverter Efficiencies reduce overall system efficiencies to 10.1% and 6.73% respectively

0%

2%

4%

6%

8%

10%

12%

14%

16%

Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov

2004 2005

Lo

ad

Fa

cto

rfaçade roof average

0

2

4

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18

Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov

2004 2005

kWh

/ m

2

Façade Roof

Load factors

Output per unit area

Little difference between orientations in winter months

Performance of PV cells

Winter Summer

Façade ~2% ~8%

Roof ~2% ~15%

• Across UK average load factor is 9 – 11% based on analysis of ROC data 2009 – 2010.

• i.e. if system is 1kW peak the average annual output will be

~ 0.1* 1 * 8760 = 850 kWh• However, solar radiation does

vary by +/-30% for one year to next.

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02040

6080

100120140

160180200

9 10 11 12 13 14 15Time of Day

Wh

01020

3040506070

8090100

%

Top Row

Middle Row

Bottom Row

radiation

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9 10 11 12 13 14 15Time of day

Wh

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Block1

Block 2

Block 3

Block 4

Block 5

Block 6

Block 7

Block 8

Block 9

Block 10

radiation

All arrays of cells on roof have similar performance respond to actual solar radiation

The three arrays on the façade respond differently

Performance of PV cells on ZICER

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8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00

Elev

ation

in th

e sky

(deg

rees)

120 150 180 210 240Orientation relative to True North 2020

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0

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6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00Time (hours)

Elev

ation

in th

e sky

(deg

rees)

January February March AprilMay June July AugustSeptember October November DecemberP1 - bottom PV row P2 - middle PV row P3 - top PV row

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Arrangement of Cells on Facade

Individual cells are connected horizontally

As shadow covers one column all cells are inactive 22

If individual cells are connected vertically, only those cells actually in shadow are affected.

Cells active

Cells inactive even though not covered by shadow

Way in which cells are connected must be considered.

Solar PhotoVoltaic: Technical Solutions:

• Inverters are only 91% efficient• Computers and other

entertainment use DC. Power packs are inefficient

• LED lighting can use DC• Need an integrated approach –

houses with both AC and DC with heat recovery from central inverter/rectifier? 23

Integrated use of PV generated energy

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Feed in Tariffs – Introduced 1st April 2010

Energy Source ScaleGeneration Tariff (p/kWh) Duration

to 31/03/2012 after 01/04/2012 (years)

Solar PV ≤4 kW new 36.1 33 25Solar PV ≤4 kW retrofit 41.3 37.8 25Solar PV >4-10kW 36.1 33 25Solar PV >10 - 100kW 31.4 28.7 25Solar PV >100kW - 5MW 29.3 26.8 25Solar PV Standalone 29.3 26.8 25

Existing PV generators transferred from RO 9 9 to 2027

On February 7th 2011, Chris Huhne announced that there would be an urgent review of PV schemes this year > 50 kW prior to the scheduled review next year – with the likelihood that such schemes would not be eligible for FITs.

However, he did state “The Government will not act retrospectively and any changes to generation tariffs implemented as a result of the review will only affect new entrants into the FITs scheme. Installations which are already accredited for FITs at the time will not be affected.” - implying at even if the degression rate is increased – those already on the scheme will not be affected.

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Feed in Tariffs – Export and Issue of Deeming

Payment for tariffs will be from a levy on Utility Companies which MAY see a cumulative rise in bills of around £1 billion or more.

In addition there will be a payment of 3p per kWh for any electricity exported as opposed to consumed on premises.

BUT an export meter is needed to identify this.

Householder will save on imported electricity at ~ 10 – 12p per kWh, so optimum financial model may not be to generate as much as possible

i.e. for each unit generated and consumed it is worth

41.3+ 12 = 53.3p /kWh for each unit exported it is worth 41.3 + 3 = 44.3 p/kWh

If no export meter is fitted – a transition arrangement of deeming that 50% of generation will be exported will be made - that may well not be as attractive to consumer.

Life Cycle Issues for PV Array on ZICER Building

Embodied Energy in PV Cells (most arising from Electricity (~80%) use in manufacture) - SPAIN

1260 1557 1073 1326

Array supports and system connections - GERMANY

135 135 135 135

On site Installation energy (UK) 52 52 52 52

Transportation between manufacture and UEA 6 trips @400 km

113 24 113 24

Total tonnes CO2 / kWp 1.56 1.74 1.37 1.51

Mono-crystalline CO2 (kg/ kWp)

Poly-crystallineCO2 (kg/ kWp)

As manu-factured

UK manu-facture

As manu-factured

UK manu-facture

Carbon Factors for Electricity Production

Spain ~ 0.425 kg / kWhUK and Germany ~ 0.53 kg/kWh

Energy Yield Ratios Life time of CellsMono-crystalline Cells 20 25 30As add on retro-fit 3.2 3.8 4.6Integrated into design 3.5 4.2 5.4

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• Solar Thermal – Installations can reduce energy requirements for hot water.– But careful consideration of timing of normal hot water system

is needed for optimum performance.

• Solar PV systems – Need care in design to ensure optimum performance. – Consider integration of use via INTERNAL DC networks to

avoid unnecessary losses.• The new Feed in Tariffs should help economics, but optimum

returns will come for early adopters.

• However:• The effective cost to society to reduce 1 tonne of CO2 in a small

scale system is over £700 tonne• < £100 per tonne for onshore wind• ~ £20 per tonne for cavity insulation

Solar Energy Possibilities: Conclusions

• This presentation will be placed on the Internet from tomorrow at:

http://www2.env.uea.ac.uk/cred/creduea.htm

N.K. Tovey (杜伟贤 ) M.A, PhD, CEng, MICE, CEnv

k.tovey@uea.ac.uk

And Finally

Lao Tzu (604-531 BC) Chinese Artist and Taoist philosopher

“If you do not change direction, you may end up where you are heading.”