Background to Solar Thermal Energy Opportunities The need for better control! N.K. Tovey ( 杜伟贤 ) M.A, PhD, CEng, MICE, CEnv 1 West Suffolk College 7 th.

Background to Solar Thermal Energy OpportunitiesThe need for better control!

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

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West Suffolk College 7th June 2011

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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)

0

1

2

3

4

5

6

7

8

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

0

1

2

3

4

5

Feb

Mar

Ap

r

May

Jun

Jul

Au

g

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Ap

r

May

Jun

July

Month

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

0

5

10

15

20

25

30

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40

45

jan mar may jul sep nov jan mar may

Syst

em E

ffic

ienc

y(%

)

bsd1

bs01

bs02

bs17

bs26

bs16

bs27

bs52

0

5

10

15

20

25

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

7

88

0

20

40

60

80

100

120

140

160

180

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

00

10

20

30

40

50

60

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80

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

Tem

per

atu

re

0

5

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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

What is needed

An auxiliary controller.

•Located between normal central heating controller and solar controller

Its function is to:

•To take predicted sunshine data from a weather source to prevent normal central heating boiler firing if adequate sunshine is likely to be available in next 2 – 3 hours.

•Bring on central heating hot water supply if no or limited sunshine or if temperature in tank is very low.

What is needed

Solar Controller

Normal Hot Water Controller

Solar Controller Sensors

Hot Water Sensors

Auxiliary Controller

Weather Information

Etc.

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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