TRIGENERATION STUDY TO INVESTIGATE THE FEASIBILITY OF PROCURING FREE COOLING FROM THE WASTE HEAT PRESENTLY REJECTED FROM AN EXISTING CHP INSTALLATION.
EPSILON CONSULTANTS (IOM) LIMITED 7 Heather Lane | Douglas| Isle of Man.
AUTHOR MICHAEL GLANFIELD CEng MEI MIET MSLL Epsilon Consultants (IOM) Limited Registered address: 7 Heather lane Abbeyfields Douglas Isle of Man IM2 7EF
Contact details: Tel: Mobile: Email: Web:
01624 677278 07624 346826 info@epsiloniom.com www.epsiloniom.com
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CONTENTS
1.0
INTRODUCTION
2.0
EXECUTIVE SUMMARY
3.0
BASIS OF CLIENT BRIEF
4.0
PREVIOUS REPORTS
5.0
DESCRIPTION OF EXISTING INSTALLATION 5.1
Heating Systems
5.2
Cooling Systems
5.3
CHP Installation
6.0
ANALYSIS AND DISCUSSION
6.1
Existing CHP Performance
6.2
Electrical Consumption Data (MSB1)
6.3
Electrical Consumption Data (MSB2)
6.4
Additional CHP Installation (Option ‘A’) 6.4.1
Additional CHP Estimated Savings (Option ‘A’)
6.4.2
Additional CHP Simple Payback (Option ‘A’)
6.5
Additional CHP installation (Option ‘B’) 6.5.1
Additional CHP Estimated Savings (Option ‘B’)
6.5.2
Additional CHP Simple Payback (Option ‘B’)
6.6
Heat Demand versus External Temperature Data
6.7
Gas Consumption Data
6.8
CHP Waste Heat vs Cooling Capacity
6.9
Adsorption or Absorption Chiller
6.10
Simple Payback Period
6.11
6.10.1
Adsorption Chiller Simple Payback (Option ‘A’)
6.10.2
Absorption Chiller Simple Payback (Option ‘B’) Adiabatic cooling
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APPENDICIES
CHARTS i.
Half-hourly Electrical Demand Charts
ii.
Daily Electrical Demand Charts
iii.
Monthly Electrical Demand Charts
iv.
Existing CHP Electrical Performance Charts
v.
Draft Electrical Load Assessment
vi.
Daily Gas Demand Charts
vii.
Monthly Gas Demand Chart
viii.
Existing CHP Waste Heat Charts (water flow)
ix.
Existing CHP Waste Heat Charts (flow & return temperatures)
x.
Existing CHP Waste Heat Charts (kwh)
SUPPLIERS & MISCELLANEOUS
xi.
Adsorption Chiller details - Weatherite Ltd.
xii.
Absorption Chiller details – Toshiba Carrier UK Ltd.
xiii.
Water Cooling details – Carter Environmental Engineers Ltd.
xiv.
Adiabatic Dry Cooler details – Transtherm Ltd.
xv.
Additional CHP - ENER-G Combined Power Ltd.
xvi.
Cogeneration & On-Site Power Production article
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1.0
INTRODUCTION Epsilon Consultants were engaged by #### to investigate and report on the potential for upgrading the existing co-generation CHP (Combined Heat and Power) plant to achieve trigeneration capability. Reports ref: #### and #### should be read in conjunction with this supplementary report.
2.0
3.0
EXECUTIVE SUMMARY a.
The existing CHP system is playing an important role in providing a low energy solution to meet the needs of the site.
b.
The existing CHP appears to possess spare electrical capacity which is not presently being harnessed to reduce the electrical operating costs of the site and is recommended to be investigated further.
c.
Any additional electrical capacity harnessed from the existing CHP shall also be reflected by a consequent increase in the quantity of waste heat generated.
d.
An additional CHP gas engine dedicated to meet the electrical demands of MSB2 would further reduce the costs of purchasing electricity for the site.
e.
Waste heat liberated by the additional CHP engine may be harnessed to displace a quantity of natural gas that is purchased to provide LTHW heating and hot water for the site.
f.
The cooling capacity of the property may be increased in the summer months by the introduction of an adsorption or absorption chiller with the primary energy being derived from the CHP waste heat presently liberated by the heat rejection equipment during the summer period.
g.
For environmental reasons Epsilon Consultants (IOM) Ltd recommend the selection of an adsorption chiller design incorporating a naturally occurring and benign dry desiccant such as zeolite or silica gel.
h.
Ongoing data logging of the CHP waste heat supply & return temperatures are recommended to be carried out in order to assist with the optimum final selection of adsorption chiller.
i.
For reasons of sound design and the elimination of the risk of legionnaire’s disease Epsilon Consultants (IOM) ltd recommend the selection of a ‘spray-less’ adiabatic design of water cooler (forming part of the adsorption chiller installation).
BASIS OF CLIENT BRIEF The remit given to Epsilon Consultants was to investigate and report on the possibility of utilising the waste heat being discharged from the CHP’s heat rejection coil or ‘heat dump’ to provide additional cooling capacity.
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4.0
PREVIOUS REPORTS The previous reports made a number of recommendations concerning the apparent lack of performance from heat station ‘3’ and for the recommissioning of the heating distribution system once the remedial works to heat station ‘3’ have been carried out. The client has recently brought to our attention the following matters which might influence the results of the original study and has requested a supplementary report to be prepared: a. b. c.
5.0
Remedial works to Heat Station ‘3’ have been carried out and completed. Technical issues concerning the metering of the main gas supply have been identified and addressed. Daily data records of gas, electricity and CHP demands are now available for analysis.
DESCRIPTION OF EXISTING INSTALLATIONS The original Mechanical, Electrical and Public Health systems were designed by #### consulting engineers, and installed by #### under sub-contract to #### who were the main Contractors for the site. The main plant area is located to the rear of the East wing and accommodates all the necessary plant and equipment required to provide all the services needs of the building, it is referred to as ‘The Energy Centre’. 5.1
Heating Systems
The heating plant consists of three dual fuel gas fired (Natural Gas)/oil fired Robey Cochrane boilers, these are configured as follows; Boiler 1 Boiler 2 Boiler 3
2.8Mw (2,800Kw) 2.8Mw (2,800Kw) 1.8Mw (1,800Kw)
Total
7.4Mw (7,400Kw)
Dependant on the fluctuations of the utilities at the time the heating plant can be switched between fuels to obtain the best value for money available at a given time. Generally the heating load is distributed via three heat stations at high temperature. These heat stations then distribute heating for both thermal comfort and domestic hot water from secondary heat exchangers to ceiling mounted radiant heating panels, air handling unit heating coils and domestic hot water systems.
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5.2
Cooling Systems
The existing cooling system consists of two roof mounted mechanical chillers, these are located on the flat roof area above the production kitchen. The chillers are manufactured by ‘Powermaster’ model FE/STRAT/LN 1603 and are rated at 423Kw each, giving a total cooling capacity of 846Kw. During construction structural provision was made for the installation of a third chiller unit. The chillers are charged electrically from a 3 phase/415v supply, the chillers are energised overnight to take advantage of the reduced rate tariff and provides chilled water to two ice storage vessels located in the energy centre, each vessel is 43 m³ in volume giving a total storage volume of 86 m³. The secondary chilled water is designed to achieve a flow and return temperature of 6°c and 12°c respectively. The chilled water circuit from the ice storage vessels serve a primary plate heat exchanger, which in turn serves the entire site. This heat exchanger is manufactured by Alfa Laval and is rated at 1603Kw 5.3
Existing CHP installation
The existing CHP Unit is a ‘Guascor’ model SFGLD480 of Indian origin and is a natural gas turbo charged generator rated at 1000 KVA1 (Alternator), as per the manufacturers technical information below: Product Specifications for Natural Gas Guascor Gensets Rated KVA Amperes Alternator Cylinder Electrical at Mechanical Engine No. of Bore Stroke Compr. Weight at Rating in Volume KW 0.8 Brake KW Model Cylinders mm mm Ratio Kg 415V.0.8 KVA Ltrs. p.f. p.f. 1
Manufacturers figures. 812 1015 1421
1000
838
SFGLD 16 480
152
165
48
11.8:1
The CHP unit was installed around June 2007; it is housed in a self-contained block work room within the Energy Centre. The associated heat rejection units are located externally at high level above the main service access doors to the Energy Centre and are interconnected to the CHP unit to enable heat rejection. This unit is configured with six fans designed to cool the heating coil, it is manufactured by Heating & Cooling Coils Ltd and has an 80mm flow and return linked directly to the CHP. This CHP unit was supplied and installed by First Energy Limited. We understand that #### have an ongoing maintenance contract for the CHP, its associated equipment, pipework and controls. The selection of a CHP unit generally falls into one of two requirements, as follows:
Sized to suit electrical energy load required Sized to suit heat load required
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8450
Other factors influencing selection include available space for plant, (which may have been the case in this instance); environmental issues such as noise nuisance to neighbours or adjacent buildings etc. ANALYSIS OF HISTORICAL DATA AND CHP PERFORMANCE 6.1
Existing CHP Performance
The bar chart (figure 6.1) shows the calculated monthly electricity cost savings for the period Dec 2012 – Oct 2013. The dark blue columns shows the savings in kwh generated units and the light blue columns takes into account other MEA charges. CHP ELECTRICITY COST SAVINGS OCT 2012 - SEPT 2013 £25,000.00 CHP SAVINGS KWH ONLY
£1,978
£6,010
£4,322
£8,768 £3,903
£3,705
£1,773
£8,189
£9,393
£11,158
Dec-12
£6,422
Nov-12
£5,845
£9,695
£5,000.00
£9,558
£8,890
£10,545
£10,000.00
£11,104
£13,381
£15,000.00
£15,711
£16,474
£19,489
£20,591
£20,000.00
£22,113
CHP SAVINGS INC OTHER CHARGES
£10,408
6.0
£0.00 Oct-12
Jan-13
Feb-13
Mar-13
Apr-13
May-13
Jun-13
Jul-13
Aug-13
Sep-13
Figure 6.1
6.2
Electrical Consumption Data (MSB1)
The bar chart (figure 6.2) illustrates the monthly electrical demands for MSB1 for the period Dec 2012 – Oct 2013. The light blue bars on the chart represent the electrical demand of MSB1 to which there is an existing CHP presently connected. The maximum electrical demand over the period Dec 2012 – Oct 2013 is 1,025kw The light blue line represents the electrical contribution made by the CHP and varies between 57 – 80% of the total electrical demand. It should be noted however that the rated electrical output of the CHP is 812kw and if fully utilised would meet approximately 90% of the electrical demand for this period. The existing CHP therefore appears to possess spare capacity which is not presently being harnessed to reduce the electrical operating costs of the site and is recommended to be investigated further. The additional electrical demands (108kva) for new works have been obtained from the M&E consultants and are represented by the dark blue bars on the chart.
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1,200
ADDITIONAL ELECTRICAL MD: 1) KEYLL DARREE EXTENSION (F) 20.0KVA 2) NICU EXTENSION (E) 45.5KVA 3) ENDOSCOPY UNIT (C) 27.0KVA 4) BREAST CLINIC (D) 15.0KVA
MONTHLY ELECTRICAL DEMANDS MSB1 DEC 2012 - OCT 2013
ADDITIONAL ELECTRICAL MD MONTHLY DEMANDS (MSB1) CHP OUTPUT
108
108
108
1,001
1013
1009
582
569
Aug-13
Sep-13
RATED OUTPUT OF CHP (812KW)
1,000 108
108
800
857
600
108
108
867
847
668
678
848
657
108
108
854
835
108
1025
108
816
691
685 635
623
599
524 400
200
0 Dec-12
Jan-13
Feb-13
Mar-13
Apr-13
May-13
Jun-13
Jul-13
Oct-13
Figure 6.2
6.3
Electrical Consumption Data (MSB2)
The light blue bars on the chart (figure 6.3) represent the electrical demand of MSB2 to which there is no CHP connected at present. The maximum electrical demand over the period Dec 2012 – Oct 2013 is 289kw The additional electrical demands (102kva) for new works have been obtained from the M&E consultants and are represented by the dark blue bars on the chart.
MONTHLY ELECTRICAL DEMANDS (kw) MSB2 DEC 2012 - OCT 2013 500
450
ADDITIONAL ELECTRICAL MD: 1) GEDDYN REESHT NEW EXTENSION (A): 72KVA 2) NEW SOCIAL SERVICES DAY CENTRE (B) 30KVA
ADDITIONAL ELECTRICAL MD MONTHLY DEMANDS (MSB2)
400 102 350
102
102
102
102
102
102
241
237
300 289 250
261
276
267
102 249
200
102
150
102
102
118
122
Sep-13
Oct-13
162
100
111
50
0 Dec-12
Jan-13
Feb-13
Mar-13
Apr-13
May-13
Figure 6.3
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Jun-13
Jul-13
Aug-13
The following table 6.3 shows the estimated maximum electrical demands for the site based upon known new works: MSB1 Existing MD Proposed MD MSB2 Existing MD Proposed MD
1025 kva 108 kva
1,133kva
289 kva 102 kva Total MD
391kva 1,524 kva
Table 6.3
6.4
Additional CHP installation (Option ‘A’)
From the information shown in table 6.3 above it is possible to make a selection of a suitable rating machine based upon the total maximum estimated electrical demands of the site. Details of a 772kw (e) natural gas powered machine and estimated costs have been obtained from ENER-G Combined Power Limited and included elsewhere in this report. In order that both the existing and additional CHP machines are loaded optimally it shall be necessary to carry out an electrical load assessment of the site in order to determine the optimum re-configuration of the LV switchboard. The exact location for the additional CHP requires to be determined but a containerised solution is presently envisaged and shall be sited as close as possible to MSB2. Heating services pipework and other mechanical works shall be required to interface the LTHW output with the existing heat stations and the cost for these works are presently excluded from this report. 6.4.1. Additional CHP Estimated Savings Summary (Option ‘A’) The estimated savings summary has been prepared by ENER-G Combined Power Ltd using the following present day energy costs and existing CHP performance values: Cost of ‘on-peak’ electricity Cost of ‘off peak’ electricity Cost of natural gas Electricity utilisation Steam utilisation LTHW utilisation Availability hours (per annum)
13.42 p/kwh 7.76 p/kwh 3.485 p/kwh 70% 70% 40% 90% Table 6.4.1.1
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Parameter Capital Electricity Savings Electricity Export Income Electricity Generation Subsidy LTHW Savings LTHW Export Income LTHW Generation Subsidy Steam Savings Steam Export Income Steam Generation Subsidy Chill Savings Chill Export Income Chill Generation Subsidy CHP Gas Cost CHP CPS Cost GROSS ENERGY SAVINGS Maintenance NET ENERGY SAVINGS (Pre Benefits) CHP Fuel CCL Benefit Add. 'Ring-Fenced' Boiler CCL Benefit Triad Saving Benefit Value of Carbon Benefit NET ENERGY SAVINGS (Post Benefits) Simple Payback Period Discount Energy Purchase Cost NET ENERGY SAVINGS (Pre Benefits) NET ENERGY SAVINGS (Post Benefits) Parameter Electricity CO2 Abatement (tCO2) LTHW CO2 Abatement (tCO2) Steam CO2 Abatement (tCO2) Chill CO2 Abatement (tCO2) Fuel CO2 Released (tCO2) Total CO2 Abatement (tCO2)
"On Peak"
"Off Peak"
£
361,433 £
£
37,668 £
£
62,466 £
(£
271,608)(£
£
189,958 £
0
"On Peak" 1,293.3 198.5 329.2 (1,431.4) 389.6
Total / Mean £ 104,498 £ 465,930 £ £ 18,834 £ 56,501 £ £ 31,233 £ 93,699 £ £ £ £ 135,804)(£ £ 18,761 £ (£ £ £ £ 0£ £ £
"Off Peak" 646.7 99.3 164.6 (715.7) 194.8
407,412) 208,719 80,000) 128,719 128,719 £ £ £ Total / Mean 1,940.0 297.8 493.8 (2,147.1) 584.5
Table 6.4.1.2
6.4.2 Additional CHP Simple Payback (Option ‘A’) Additional CHP (MSB2) Supply & delivery (ENER-G Combined Power Ltd) Weatherproof acoustic enclosure Installation & Commissioning Ancillaries Total estimated cost * Budget costs
£459,000* £75,000* £125,000* £15,000* £674,000
Total estimated capital cost Annual estimated energy savings (see table 6.4.1.2) Simple payback
£674,000 £128,719 5.25 years
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6.5
Additional CHP installation (Option ‘B’)
Figure 6.5
From the information shown in figure 6.5 above it is possible to make a selection of a suitable rating machine based upon the base load electrical demands of electrical switchboard ‘MSB2’ and include an allowance for the estimated electrical demands for the new developments. Details of a 230kw (e) natural gas powered machine and estimated costs have been obtained from ENER-G Combined Power Limited and included elsewhere in this report. The CHP suppliers have advised that it is uneconomic on smaller rated CHPs to recover the high grade heat from the engine exhaust for the purposes of generating steam via a waste heat boiler. Savings in steam mitigation have therefore been excluded from the savings summary. In addition it may be seen from the savings summary that operating the CHP in “off-peak” hours produces a net loss so the unit should only run during “on-peak” periods. The maintenance price reflects running in the peak time only, however, if the electricity tariffs become more favourable so that running in the off-peak period can provide useful savings then the CHP maintenance costs will also increase accordingly. The exact location for the additional CHP requires to be determined but a containerised solution is presently envisaged and shall be sited as close as possible to MSB2. Heating services pipework and other mechanical works shall be required to interface the LTHW output with the existing heat stations and the cost for these works are presently excluded from this report. The suppliers’ budget capital cost for a 230kwe CHP include for the following items only:
ENER-G 230 genset; Low noise weatherised container rated to 65dBA @ 1m; Low noise heat rejection radiator rated to 65dBA @ 1m; Air fuel ratio controller and catalyst for low NOx emissions; Low noise silencers; P a g e | 11
Power modulation panel; DRV and 3 port valve for lower than 90°C flow and 80°C return; Gas and heat meters; G59/2 application fee; Supply, delivery and commissioning only.
6.5.1. Additional CHP Estimated Savings Summary (Option ‘B’) The estimated savings summary has been prepared by ENER-G Combined Power Ltd using the following present day energy costs and following CHP performance values: Cost of ‘on-peak’ electricity Cost of ‘off peak’ electricity Cost of natural gas Electricity utilisation Steam utilisation LTHW utilisation Availability hours (per annum)
13.42 p/kwh 7.76 p/kwh 3.485 p/kwh 100% n/a 40% 90% Table 6.5.1.1
Parameter
"On Peak"
Capital Electricity Savings LTHW Savings CHP Gas Cost GROSS ENERGY SAVINGS Maintenance NET ENERGY SAVINGS Parameter Electricity CO2 Abatement (tCO2) LTHW CO2 Abatement (tCO2) Fuel CO2 Released (tCO2) Total CO2 Abatement (tCO2)
£153,450 £37,668 (£131,479) £59,638
"On Peak" 549.1 198.5 (692.9) 54.7
"Off Peak"
Total / Mean £ £44,366 £197,816 £18,834 £56,501 (£65,740) (£197,219) (£2,540) £57,098 (£20,000) £37,098 "Off Peak" Total / Mean 274.5 823.6 99.3 297.8 (346.4) (1,039.3) 27.4 82.1
Table 6.5.1.2
6.5.2 Additional CHP Simple Payback (Option ‘B’) Additional CHP (MSB2) Supply & delivery (ENER-G Combined Power Ltd) Weatherproof acoustic enclosure Installation & Commissioning Ancillaries Total estimated cost * Budget costs
£210,000* £50,000* £100,000* £10,000* £370,000
Total estimated capital cost Annual estimated energy savings (see table 6.5.1.2) Simple payback
£370,000 £37,000 10 years
Table 6.5.2.
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6.6
Heat Demands versus Average External Temperatures
The following chart (figure 6.6) shows the daily average external temperatures plotted alongside the daily heat demands for the site for the month of January 2013. N.B. historical temperature records for the months of analysis were obtained from the nearest weather station website. As may be seen the temperatures rise and fall in a wave effect during the month of January 2013. The heat demand chart would be expected to show an approximate converse shape owing to the BMS controlling the output of the boilers to meet the heating demands of the site. This finding may require some further investigation carried out on the building management system to ensure that the optimisation feature of the BMS is functioning properly.
Figure 6.6 Heat Demand vs Average External Temperature Chart Jan 2013
6.7
Gas Consumption Data
The heat generated by the CHP in day to day operation is sometimes referred to as ‘free heat’ because it is a by-product of the generation of electricity. The light red coloured bars on the chart represent the amount of gas consumed by the CHP for generating electricity and heat and the deep red coloured bars represent the quantity of gas consumed by the heating boilers for meeting the LTHW heating, domestic hot water and process steam demands. As can be seen from the following chart (figure 6.7) the heat output from the CHP is reasonably consistent for the latter part of the month of January 2013 and accounts for approximately 40% of the total heat demand for the site. In March 2013 the CHP contributed 36% of the total heat demand and in May 2013 the CHP contributed 48% of the total heat demand. Minimum and maximum external temperatures have been overlaid on the gas consumption charts for informational purposes only. For the same reasons discussed in 6.6 above one would expect to see a fairly close correlation between the heating demands and recorded external temperatures. P a g e | 13
Figure 6.7 Gas Consumption Chart January 2013
CHP Waste heat vs Cooling Capacity The monthly gas demands (figure 6.8.1) show that demands for heat from the main boilers is significantly reduced in the summer months. By comparing the excess heat chart for August 2013 (figure 6.8.2) shows that a significant amount of the heat energy supplied by the CHP is presently being liberated to the atmosphere rather than being put to any useful purpose. MONTHLY GAS DEMANDS (kwh) NOV 2012 - JULY 2013 4,000,000
CHP ELEC
3,500,000
CHP ELEC
CHP HEAT
CHP ELEC CHP HEAT BOILERS + STEAM
CHP ELEC CHP HEAT BOILERS + STEAM
CHP ELEC CHP HEAT
CHP ELEC
CHP HEAT
CHP ELEC
BOILERS + STEAM
500,000
BOILERS + STEAM
1,000,000
BOILERS + STEAM
1,500,000
CHP HEAT
2,000,000
BOILERS + STEAM
CHP ELEC
BOILERS + STEAM
CHP HEAT
2,500,000
CHP HEAT
3,000,000
BOILERS + STEAM
6.8
0 Nov-12
Dec-12
Jan-13
Feb-13
Mar-13
Figure 6.8.1
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Apr-13
May-13
Jun-13
Jul-13
EXCESS CHP HEAT (M3) TO HEAT REJECTION PLANT AUG 2013
WATER VOLUME 900
830
818 818 818
807
780
800
700
25
MEAN EXTERNAL TEMP 802 801 798 800 800 800 805 805 796 804 801 801 801 799 803 798 800 799 799 799 799
788
808 799
20
679
600 15 500
400 10
300
200
5
100
0
0
Figure 6.8.2
Suppliers of packaged cooling equipment have advised that both the temperature and flow volume of the CHP waste heat for the period under analysis represents sufficient energy for either an absorption or adsorption chiller to provide an additional 423kw of cooling capacity. Ongoing data logging of the CHP waste heat water flow and supply & return temperatures are recommended to be carried out further in order to assist with the optimum selection of chiller. 6.9
Adsorption or Absorption Water Chillers?
An article reprinted from the September 2009 online edition of Cogeneration & On-site Power Production provides an excellent description of the modes of operation, benefits and drawbacks of both adsorption and absorption water chillers (see appendices). In summary the adsorption machine incorporates a dry desiccant in the form of naturally occurring and environmentally benign zeolite or silica gel and the absorption design utilise a liquid desiccant in the form of lithium bromide which is not environmentally benign. For reasons of environmental sustainability Epsilon Consultants (IOM) Ltd recommend the selection of an adsorption chiller utilising zeolite or silica gel as the desiccant. A significant cost premium is attached to the adsorption chiller for reasons of the design being not so well established and relatively few machines having been supplied. The adsorption design also requires a chilled water buffer vessel to be incorporated owing to the production of chilled water being intermittent. Proposals have been received from suppliers of both types of chiller designs and are included elsewhere in this report. The suppliers of the adsorption chiller (Weatherite Ltd) have advised the following details (table 6.9.1) concerning the estimated electrical demands of the equipment parasitic loads:
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ADSORPTION CHILLER PRIMARY PUMPS CHW SECONDARY PUMPS CHW PRIMARY COOLING PUMPS SECONDARY COOLING PUMPS HOT WATER PUMPS COOLING TOWER FANS
0.2 KW 7.5 KW 7.5 KW 30.0 KW 18.5 KW 18.5 KW 22.0 KW
TOTAL CONNECTED LOAD
104 KW
TOTAL RUNNING LOAD
60 KW
Table 6.9.1
The estimated costs for the supply of both types of chillers exclude the following items:i. Offloading costs (crane & temporary storage) ii. Adiabatic dry cooler iii. Pumps, fans & controls iv. Small air compressor v. Installation vi. Pipework interface with existing systems vii. BMS interface viii. Weatherproof container or enclosure 6.10
Simple Payback Calculation
The following are simple payback calculations based upon the estimated capital costs for both chiller types and the electricity tariffs currently in force: 6.10.1 Option ‘A’ Adsorption chiller (Weatherite + Dry Cooler) Adsorption Chiller Supply & delivery (Weatherite Ltd) Adiabatic dry cooler (Carter Env Engineers Ltd) Installation & Commissioning Ancillaries Total estimated cost * Budget cost Annual energy costs saved 1 M3 of ice storage = 93kwh. 43 M3 = 4,000kwh = 9.45hrs charging 8 hours x off-peak rate (£0.0776) x 423kw x 274 hours* 1.45 hours x on-peak rate (£0.1342) x 423kw x 274 hours* Less parasitic demands for adsorption chiller: 8 hours x on-peak rate (£0.1342) x 60kw x 274* Net annual saving Assume 9 months per annum cooling cycle Simple payback calculation Total estimated cost Annual estimated running cost £94,505 Less parasitic demands £17,650 Simple payback
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£195,000 £126,000 £50,000* £15,000* £386,000*
£71,952 £22,553
£94,505
£17,650 £76,855
£386,000 £76,855 5 years
6.10.2 Option ‘B’ Absorption chiller (Toshiba Carrier + cooling tower) Absorption Chiller Supply & delivery (Toshiba Carrier Ltd) Forced draft cooling tower (Carter Env Engineers Ltd) Installation & Commissioning Ancillaries Total estimated cost * Budget cost Annual energy costs saved ** 1 M of ice storage = 93kwh. 43 M3 = 4,000kwh = 9.45hrs charging 8 hours x off-peak rate (£0.0776) x 423kw x 274* 1.45 hours x on-peak rate (£0.1342) x 423kw x 274* Less parasitic demands for absorption chiller: 8 hours x on-peak rate (£0.1342) x 60kw x 274* Net annual saving Assume 9 months per annum cooling cycle
£75,000 £35,000 £25,000* £15,000* £150,000*
3
Simple payback calculation Total capital estimated cost Annual estimated running cost £94,505 Less parasitic demands £17,650 Simple payback
£71,952 £22,553
£94,505
£17,650 £76,855
£150,000 £76,855 2 years
** The saving in electricity running costs may be calculated as the annual cost of electricity that would be paid by providing an additional 423kw electrical chiller and ice storage vessel of the same specification as presently exists. 6.11
Adiabatic cooling
It should be noted that both adsorption and absorption chiller designs require a cooling tower (forced draft or induced draft) or an adiabatic dry cooler to be incorporated into the installation in order to reject the low grade heat from the condenser cycle. A water operated cooling tower of either forced draft or induced draft design presents an inherent risk of legionella unless a properly managed maintenance regime is implemented. A ‘sprayless’ design of adiabatic dry cooler, however, does not carry an intrinsic risk of legionella because of the closed circuit type of design although there is a premium to pay in terms of capital costs and running costs. Budget proposals have been received from Carter Environmental Engineers for various specification water towers and adiabatic dry coolers and cooling towers are included elsewhere in this report. For reasons of the elimination of the risk of legionella Epsilon Consultants (IOM) ltd recommend the selection of an adiabatic dry cooler.
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