Transcript
Commercial Buildings Special Working Group
Assessment of Commercial Buildings Report with sample sites.
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Table of Contents 1.
Introduction ....................................................................................................................................................................................... 1
2.
General Site Description................................................................................................................................................................ 1 2.1.
Building A .............................................................................................................................................................................. 1
2.2.
Building B. ............................................................................................................................................................................. 2
3.
Scope & Methodology ................................................................................................................................................................... 2
4.
Site A..................................................................................................................................................................................................... 3 4.1.
Past and present energy use and baseline assessment ....................................................................................... 3
4.2.
Areas of significant energy use ..................................................................................................................................... 6
4.3.
Differences between current operational practices and identified best practice ...................................... 6
4.4.
Differences between current maintenance practices and identified best practice ................................. 11
4.5.
Potential savings to be achieved from the changes in operational and maintenance
practices 13 5.
Site B ................................................................................................................................................................................................... 13 5.1.
Past and present energy use and baseline assessment ..................................................................................... 13
5.2.
Areas of significant energy use ................................................................................................................................... 17
5.3.
Differences between current operational practices and identified best practice .................................... 18
5.4.
Differences between current maintenance practices and identified best practice................................. 18
5.5.
Potential savings to be achieved from the changes in operational and maintenance
practices 20 6.
7.
Recommended methodology to assess impact of changes made ............................................................................. 20 6.1.
Site A ..................................................................................................................................................................................... 21
6.2.
Site B ..................................................................................................................................................................................... 21
Conclusion........................................................................................................................................................................................ 22
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Table of Figures Figure 6: Comparison of consumption Summer to winter ........................................................................................................ 4 Figure 7: Comparison of consumption to weather (CDD Base 6 ) ........................................................................................... 4 Figure 8: Comparison of Natural gas consumption to weather ............................................................................................... 5 Figure 9: Weekly consumption of energy......................................................................................................................................... 6 Figure 10: Temperature profile of one area overnight ................................................................................................................ 8 Figure 11: Temp profile area 2 overnight ......................................................................................................................................... 8 Figure 12: Temp profile area 3 overnight ......................................................................................................................................... 9 Figure 13: Sample consumption shown against a profile including a standard weekend .......................................... 10 Figure 14: Sample consumption against a profile including Xmas day .............................................................................. 11 Figure 1: 15 minute profile for sample days during the year .................................................................................................. 14 Figure 2: Comparison of Electrical use to degree days (Base 20.5) ....................................................................................... 15 Figure 3: Comparison of night consumption to weather (Base 20.5).................................................................................. 15 Figure 4: Average day of week night load ...................................................................................................................................... 16 Figure 5: Average day of week day load ......................................................................................................................................... 17
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1. Introduction The purpose of this report is to assess a small sample of buildings operational and maintenance practices with respect to the operational and maintenance practices recommended in the SEI O&M best practice manual written by the commercial buildings special working group 2010.
The purpose of the O&M manual was to identify the best practice O&M practices that an organisation should implement to ensure that the energy usage of their commercial buildings is optimised without negative impact on reliability, comfort or services provided.
The report does not include the actual current practices undertaken but assesses the gaps between that and best practices to provide an insight to what is typically overlooked when commercial buildings operational and maintenance programs are put together from purely an operational and reliability perspective.
2. General Site Description The sample buildings selected for this report are two buildings owned by entities that provide services directly to the public but neither building has public access on an ongoing basis. The buildings have their own issues and will be addressed separately in this report. For the purpose of the report the operational and maintenance practices will be addressed separately and we have selected two buildings as a subset of the buildings assessed in this review
The O&M manual is solely written to address operational and maintenance practices within the buildings. Whilst reference may be made periodically to alternative systems that might have been used to provide the service provided by equipment within the buildings in question, this will not be examined in detail as the focus of this report is not to carry out a typical energy audit and identify potential new technologies that may be used to replace existing systems.
2.1. Building A Building A is an operations centre for a financial services company based in Dublin. The building provides operational support to a larger network by providing a range of financial services within the building. The building was originally a single storey building , flat roof construction built in the 1960’s and this was extended in 1999 with a three storey building consisting of three operational floors and the top floor providing services to the building.
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As a commercial building in the financial services sector, the services required within the building are primarily based about space conditioning and occupant comfort. The building owner has identified the areas of significant energy use within the building as being HVAC, Chilled water, boilers, and domestic hot water. A and B block services differ slightly as both have their own dedicated LPHW, DHW and HVAC services.
“A” block has a centralised HVAC system with chiller and LPHW services generated locally to the chiller either within the plant room or on the adjacent rooftop. DHW services are generated locally by undersink heaters. A block services are controlled by its own building management system.
B block HVAC requirements are delivered by their own independent HVAC self contained units with their own dedicated controller. There is also a dedicated natural gas boiler that generates the hot water services for B block including the canteen and radiator circuits.
2.2. Building B. Building B is a multi-functional building within the data services industry. The building houses data network services, maintenance, data network support, telephone call centre and general administrative functions. This building has a mixture of building services varying from L:PHW radiator circuits, split air conditioning units to electrical storage heating, all manually and timer based controlled.
3. Scope & Methodology The scope of this work is to carry out an assessment of the potential impact of the use of the SEAI Commercial Buildings Special Working Group operations and maintenance report by owners and users of commercial building and therefore to assess its potential usefulness to the commercial buildings sector.
The methodology used in this assessment was to first discuss the type of building with the building owner/ client and identify the areas of significant energy users within the building and approximate breakdown of energy use within the sites. At this point a site visit was undertaken to assess the current operational and maintenance practices and the gaps that could be identified between existing practices and the practices outlined in the O&M report. For practical purposes this assessment has been broken into separate operational gaps and maintenance sections.
Using the sites energy data provided by the building owners, analysis of this data allowed the sites energy baseline to be identified along with any identified factors. 2
Having identified this baseline, the gaps in the current and proposed O&M practices were assessed for practicality to see which of these practices are suitable to be put into practice on the sites and in cases where best practice is not proposed to be put in place an identifying reason for this decision.
From this an assessment of potential savings has been made to allow the sites to gain an understanding of what the potential benefit would be of the change in O&M practices to allow them to make a best case assessment of the cost and benefits of undertaking these changes in view of any issues such as IR issues, training requirements, competence assessments, perceptions on site and change management issues.
The energy baseline previously identified now allows the site to utilize this baseline as a means of assessing the real impact of changes implemented. This is in effect the real assessment of the impact of the report as it identifies the savings that have been made resulting from the client interactions with SEAI.
4. Site A 4.1. Past and present energy use and baseline assessment The primary fuel consumption of the financial services building is Electricity with Natural gas being used as the secondary fuel.
The total electrical consumption of the building for the year 2009 was approximately 2.6GWh and the total gas consumption for 2009 was approximately 1.1 GWh.
Assessing the baseline for the building required review and analysis of the profile of consumption and this report will show a small portion of the analysis undertaken. Initial analysis indicates that the building consumption is relatively constant and showing that summer consumption would appear to be higher.
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Comparison Electrical kWh Summer and winter 10,000 8,000 6,000
Sample Week Jan
4,000
Sample Week June
2,000 ‐ 1
2
3
4
5
6
7
Figure 1: Comparison of consumption Summer to winter
Comparison of electrical usage to weather shows little correlation as seen in the diagrams below, something which might not be expected in a commercial building such as this. The reason we expect to see a better relationship between weather and electrical consumption is that the other main electrical users in the building appear to be relatively constant load devices, with a relatively consistent profile of operation.
kWh elect v/s CDD base 6.5 deg 225000 220000
kWh
215000 210000
y = 46.934x + 196323 R² = 0.20615
205000
total
200000
Linear (total)
195000 190000 185000 0
50
100
150
200
250
Cooling Degree Days Figure 2: Comparison of consumption to weather (CDD Base 6 )
The initial indication of this would be that there is very poor control of electrical consumption in HVAC as we would expect to see better correlation to weather to some extent either heating or cooling
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considering there is no humidity control. This is especially the case where HVAC has been identified as an area of significant energy use
The same assessment was undertaken with different base temperatures and the profile shown displayed the best correlation of result.
When we assess the gas consumption however and normalise consumption against weather we see a stronger correlation.
180,000
y = 348.2x + 24816 R² = 0.85185
160,000 140,000
kWh
120,000 100,000 80,000 60,000 40,000 20,000 ‐ ‐
50
100
150
200
250
300
350
400
HDD ‐ 15.5 Figure 3: Comparison of Natural gas consumption to weather
This indicates reasonably control of the HVAC system and therefore indicates that gas savings can be analysed against this normalised consumption.
Electrical consumption cannot therefore be analysed against weather however and we must find another established baseline.
The best baseline that appears to work for consistency of consumption is weekly consumption of electricity which is seen below. Eliminating the first and last year and making an exception for one devient point shows an average error of approximately 2.8% from the baseline of 50,246 kWh/week. This we shall use as the baseline for consumption against which to assess savings made.
Again reviewing the electricity consumption and the fact that it does not correlate in any way to weather, coupled with the fact that gas usage and therefore heat appears to be relatively closely controlled. This
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would appear to point to the chiller plant, and in particular the control of this unit being an issue for consideration.
Weekly consumpCon 30000 25000 20000 15000 10000
0
1 15 29 43 57 71 85 99 113 127 141 155 169 183 197 211 225 239 253 267 281 295 309 323 337
5000
Figure 4: Weekly consumption of energy
4.2. Areas of significant energy use The areas of significant energy usage within the Bank of Ireland facility are identified as the following. 1.
HVAC
(total 31% between boilers and chillers)
2.
Chillers
3.
Boilers
100% gas
4.
Lighting
14% rating by client
5.
General services 26%
6.
Clean power
29%
4.3. Differences between current operational practices and identified best practice A number of areas were identified where best practices could be implemented to reduce energy consumption. With the short duration of the site visit it must be assumed that operational practices identified are typical of normal operation and order of magnitude savings estimated on this basis.
1.
“A” Block fan coil units are supplied with a continual hot and cold supply where the requirement
for a hot supply in summer and a cold supply in winter could not be identified. This appears most likely to be a controls related issue where additional heating is required to guard against a potential lack of control in overcooling and vice-versa.
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Where dehumidification is not required it should be possible to identify seasons where heating is not required and potentially seasons where cooling is not required.
2.
In “A” Block, for a number of the open office areas, it was identified that a significant number of
the sensors controlling the fan coils had cooling induced unnecessarily due to the sensor location being to the rear of a hot source of air at the back of printers, fax machines etc. The source of the problem could be eliminated by moving of the printers etc or alternatively movement of the sensor to a more appropriate location.
3.
The Randamax Boilers in “A” Block are of the 2000 range and do not appear to be of the
condensing type. They do however appear to have the facility on their control units to have seasonal settings for summer and winter operation. This being the case, this would allow the set points of the boilers to be adjusted to allow for lower set points in summer when there is a limited need for heat. The set point on the day was 70 degree C which would appear to have the potential to allow a reduction to approximately 60 deg C.
4.
The Chillers supplying chilled water to the air handling units operate on a primary secondary
loop system with all loops unnecessarily pumping water about the circuits once the services are operational. There is the potential for a number of these pumps to be shut down when not required – possibly based on temperatures in some spaces or seasonally.
5.
The operation of the heat recovery system between extract and supply AHU’s would require
questioning as with Irish ambient temperatures and the temperature of the extracted air, it is questionable as to whether the heat recovered outweighs the additional power requirements of pumping air through the back pressure that the coils represent.
6.
The control of some instrumentation and indeed the quality of the sensor inputs to the HVAC
control equipment may be questioned. With an external temperature of 14 degrees, air taken in from outside the building was seen on the BMS to have a temperature of 18 degrees, and require the cooling valve to be at a 30% open position to achieve a duct supply temperature of 16.5 degree. 7.
The requirement of air flow to the rooms may be questioned based on an observation of the size
of the ducting, and the fact that the systems should only require to supply ventilation air only. This should at the least allow a set-back routine for portions of the day/ evening operation.
8.
The timers of the starting and stopping of the significant energy using equipment and its day
and night operation should be closely examined. To examine the reality of the system operation compared to the times that equipment was said to be operational, temperature profiles in various spaces 7
were viewed on the building management system and compared to what we would have expected to see. A number of anomalies were observed.
Figure 5: Temperature profile of one area overnight
Figure 6: Temp profile area 2 overnight
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Figure 7: Temp profile area 3 overnight
All appear to show the following characteristics •
Rapid temperature rise in the room at a particular point in time – this suggests that chillers are being isolated and the space being actively heated for a period of time before heating being isolated.
•
Gradual ramp up in temperature over a period of time – this suggests that there is significant heat gain in the space – Can we ensure that the maximum amount of equipment contribution to heat gain is switched out at night.
•
Rapid cooling down of space temperature – this suggests that either cooling is becoming active or there is some ventilation event occurring when the building is out of operation – the cause of this was not identified. It does not appear to be an upper threshold of temperature driving on chiller plant or HVAC plant.
•
Accelerated heat up of spaces in early morning, possibly due to heating becoming active before other elements of HVAC, or alternatively fan coils being active with central plant off.
•
Period of controlled temperature at a high level.
•
Rapid cooling to the lower base temperature.
•
Onset of controlled temperature fluctuations.
This appears to point to potential for improvements in timing of equipment on and off and also improved controls to allow temperature controls to be held closer to the upper and lower dead-bands with reduced energy consumption. 9
When we look at the profile of electrical consumption at nights we can see a suggestion that there remains some significant equipment switched on with swings in power consumption at times. This would not be expected with a system where the important equipment would be backed by UPS and therefore on a more regular consumption profile.
8.
The BMS controlling the building could have an optimiser feature initiated to allow the plant to
learn the building response over time and eliminate the need for fixed equipment start and stop times replacing these with start and stop times related to current building and external conditions.
9.
Large areas of building lit apparently unnecessarily. Large banks of switches unlabelled.
10.
Weekend consumption of energy being 40% of a typical weekday consumption, this would
indicate that there is potential for switching out of equipment at weekends. This shows a difference in the order of 11% between weekend consumption at Christmas and that on regular weekends. If we take this as being an impact of stitching down unessential services over the days of Christmas that might also be switched out on regular nights and weekends this would offer a significant saving.
600 500 400 300 200 100 0 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 Figure 8: Sample consumption shown against a profile including a standard weekend
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700 600 500 400 300 200 100 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 Figure 9: Sample consumption against a profile including Xmas day
11.
The absence of any reasonable correlation of electrical consumption to weather suggests that
the HVAC control system for cooling in block B might well be fighting the radiator circuits to control the temperature in the areas. It was not possible to access control on the day to assess these. There is most likely the potential to either switch these units off in winter or alternatively to ensure that they are set to operate in cooling mode only.
4.4. Differences between current maintenance practices and identified best practice For the areas of significant energy usage we assess some current maintenance practices versus best practice. It was not possible to access records of actual maintenance as maintenance is carried out by an external company that was not available at the time of the review.
1.
The HVAC units are assessed by type but the approach is common. The maintenance is
proposed on the lines of checking and changing filters and assessing actuators for correct operation.
This should further include the assessment of the HVAC unit in totality for prudent operation, taking into account internal and external temperatures, and monitoring the temperatures (humidity as appropriate) of the air as it passes through the unit. This requires access to the BMS screen and a good understanding of psychometrics where humidity is involved. What should be particularly looked for is unnecessary simultaneous heating and cooling.
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Where mention is made in the maintenance routines of evaporator and condenser temperatures, these should be assessed to ensure that the approach temperature is not excessive and record this. Where HVAC is supplied by multiple cassette type units (Block B) consideration should be given to assessment of the impacts of one units operation against another.
2.
Boiler heating system maintenance requirement makes reference to assessing air fuel ratio, but
does not make any clear recommendation on excess air level that is correct/ incorrect. No mention is made on assessment of insulation on boiler and plant/ piping surrounding. No mention is made of what the appropriate temperature is for LPHW, or the potential to float temperature for times of the year and seasonal load.
3.
Chillers maintenance makes assessment of basic operation, but not appropriate operation for
prevailing conditions. This should recommend Chilled Water set point delivery and acceptable return temperature. It should also make reference to acceptable maximum condenser temperatures and minimum evaporator temperatures.
4.
Building management system makes reference to ensuring correct control is maintained and
values are realistic. This should also make mention that values for control make maximum use of deadband to minimise energy consumption. It should also require an assessment to be made of all timings of equipment starts and assessment of systems that interact with one another.
5.
Lighting maintenance makes reference to visually inspect and repair as necessary. This should
make reference to assessment of areas lit where not required or over-lit, potential for improved switching to ensure proper use is possible, potential for use of timers or occupancy sensors and make reports to where it is believed that lighting is operated unnecessarily.
6.
There appears to be no maintenance undertaken on domestic hot water. Mention was made
during the visit of some DHW being heated by electricity, no assessment of appropriate temperature level for energy efficiency perspectives.
7.
Consider the addition of a paragraph to all procedures to request any identified opportunities
for energy reduction or improved maintenance to be forwarded with the completed maintenance report.
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4.5. Potential savings to be achieved from the changes in operational and maintenance practices With Site A, the suggestion is that whilst maintenance changes will lead to energy savings by the identification of otherwise unnoticed opportunities, the stronger opportunities lie in the operational area. For example when we assess the lighting consumption of the offices in terms of a typical lighting density for offices of 10.76W/M2, the floor area of the building and a typical operational hours of 3000hrs/yr this gives a usage of 10% of the energy consumption of the building. This compares with the identified amount of 14% as per client data. (The 10% was calculated on a reasonably representative figure for office lighting density and operating hours.
During the visit it was noted that the chiller plant condenser temperatures appeared high (in the region of 40 deg). This would indicate that there is potential for relatively significant savings to be made on chiller electrical usage. This would need to be also checked on the units controlling cooling on Block B which was not accessible during the visit but it is expected this will be similar.
It is expected that savings in the region of 15% could be made by closer operational control linked with the current maintenance being slightly modified to take account of energy efficiency. In particular it is expected that the majority of savings are likely to be delivered by better use of space heating, probably through the widening of dead bands and use of sensor information from valid sensor locations.
5. Site B 5.1. Past and present energy use and baseline assessment The primary fuel consumption of Site B is Electricity. There is a small amount of oil utilised to supplement heat to the building to assist in raising the temperature of the building in winter but this is small in comparison to the electrical consumption. For this reason the focus of the visit is placed on electricity consumption.
The total electrical consumption of the building for the year May 2009 to April 2010 was approximately 1.06GWh. Assessing the baseline for the building required detailed review and analysis of the profile of consumption and this report will show a small portion of the analysis undertaken. One feature of the profile for the building was a double peak in consumption, one occurring shortly after midnight and the other after mid-day ( a conventional peak). This is shown in Fig 1 below.
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Comparison of daily 30 min load profiles 250
200
kW
150
100
50
0
25/12/2009
22/06/2009
21/12/2009
Figure 10: 15 minute profile for sample days during the year
The profile shown is explained by the fact that storage heaters are utilised to heat the building, with the storage elements “charging” overnight. It should be noticed that the profile for Christmas day very closely matches that of the previous Monday which indicates that the building has a relatively constant electrical consumption. The double peak does not occur to any real extent in summer and this is explained by the fact that the storage heaters are not operated in summer, being manually switched out of service.
Analysis of the electrical consumtion against weather showed strong correlation at a base temperature of 20.5 deg C.
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kWh total v/s Degree Day (normalised) Base 20.5 y = 46.822x + 72372 R² = 0.79323
100000
kWh
80000 60000 40000 20000 0 0
50
100
150
200
250
300
350
400
Degree Days Figure 11: Comparison of Electrical use to degree days (Base 20.5)
When we consider the fact that storage heater “charge” is done at night, we furthe look at the night consumption versus weather and we see an even stronger relationship. Other base temperature assessments showed the relationship to be stronger at this temperature indicating that the building temperature control may have potential for reduction. (all details have been normalised) This would be done by reducing the output setting of the storage heaters or the temperature set-point for storage. When we analyse daytime energy consumption versus weather we see a flat relationship indicating that the daytime electrical consumption is indepependant of weather. This links well with the fact that there is consistent cooling for the connected data handling equipment and split AHU’s used for heating and cooling requirements.
kWh/ month ‐ normalised
kWh night v/s degree days Base 20.5 (normalised) y = 35.293x + 18122 R² = 0.91649
40,000 30,000 20,000 10,000 ‐ 0
100
200
300
400
500
Degree Days/,month ‐ normalised ‐base 20.5
Figure 12: Comparison of night consumption to weather (Base 20.5) 15
600
When we further take account of the split between night and day consumption this leads us to compare daily consumption and this shows some interesting features. The average night load shows a slight fall off in night consumption at weekends of approximately 3%, possibly due to less building activity leading to less heat loss, but also possibly a reduction in night time activity in call centres etc.
Average Night load 1,060 1,055 1,050 1,045 1,040 1,035 Mon
Tue
Wed
Thu
Fri
Sat
Sun
Series1 Figure 13: Average day of week night load
When we look at the average day time load we see a slightly larger fall off in consumption at weekends althought it is still noticeable that the overall day consumption only falls by 10% for weekends and Friday has a small reduction also.
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Average Day Load 1950 1900 1850 1800 1750 1700 1650 1600 Monday
Tuesday
Wednesday Thursday
Friday
Saturday
Sunday
Figure 14: Average day of week day load
Assessment of the standard deviation from the mean for day and night for daily loads shows that there is a larger variation in the night load –This is to be expected reflecting summer and winter variations in heat requirement, but less variation in daytime consumption, again indicating a consistent load. The standard deviation from the mean consumption for day by day consumption is in the order of 5-6% It is recommended that we utilise the base line for night consumption (relationship to degree days) to assess the impact of any proposed improvements to the storage heater, and utilise the average daily load values of consumption for day time operation as our baseline to assess improvements for others.
5.2. Areas of significant energy use The areas identifies as being of significant energy usage for the data handling facility are as follows:
1.
Directly connected data equipment, including un-interruptible power supplies etc.– This is
typically seen as a base load consisting of the power requirements of the data equipment and represents approximately 43% of the electrical power consumption of the building.
Review of this type of
equipment confirmed that the power draw from the data equipment is relatively constant. 2.
HVAC Chiller Load. – This represents 20-25% of electrical energy load
3.
General Services – including computing and lighting – approximately 20%.
4.
Storage heating (Approximately 7%)
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5.3. Differences between current operational practices and identified best practice The control of the building assessed was primarily manual, and the operational practices seen on site appear to be quite good reflecting a good overall knowledge of the nature of the energy impacts of operations. A small number of improvements have however been identified.
1.
There appeared to be a number of areas not in use to any great extent and despite only
occasional use will be heated during winter months. It is recommended that all unused/ areas with occasional use only be clearly signed accordingly and not maintained to the same levels as other spaces. The temperature control in these areas should be for building/ fabric protection only.
2.
The space heating requirement of the building is significant and it is expected that a minimum
of 90 minutes could be shaved off the “charge” time of the units in incremental periods. It is possible that this may also be achieved using a form of integrator or optimiser unit but it is thought that the manual method should be initially trialled.
3.
The standby generator for emergency power has an oil pre-heater active permanently to
provide for “smoother” or “less risky” engine starting. Whilst oil pre-heating does indeed reduce the wear and tear on the engine on start up, an engine of this size has no requirement for this preheating.
4.
One particular area has a printer located in it for occasional use. The space is generally
unoccupied and this can cause the space to be lit for long periods of time unnecessarily due to users not switching out lighting after use. It is recommended that the printer be re-located or lighting re-zoned to ensure that only the necessary area is lit for printer.
5.4. Differences between current maintenance practices and identified best practice The principle aim of maintenance within the building is reliability and maintenance of service – energy not really considered. Review of the supplied service specifications leads to the following observations related to the areas of significant energy use identified.
1.
Maintenance of Power Factor Correction Capacitors does not contain a review of historical
electrical consumption on site to indicate periods of inadequate PFC. Electrical checks only check equipment is operational and not whether suitable for application as changes may have occurred in building. Are the switching levels of the capacitor banks appropriate? 18
2.
Lighting – Service specification makes reference to replace lighting as required. It makes no
reference to reducing lighting levels in areas where existing levels are not required. It makes no reference to ensuring all fittings used are electronic ballast, or any other indication of what form of light considered acceptable or otherwise. Suggest ion is made also to check the adequacy of switching arrangements and potential to replace manual switches with manual push timers in all small areas and potential for occupancy sensors in others.
3.
Storage Heaters – makes reference to ensuring that time clocks are correct. No referenceis
made to what the correct setting should be, nor to ensure that storage heaters in areas unused are taken out of service.
No mention made of assessing the correct mechanism of a sample number of
thermostatic devices on the storage heaters.
4.
AHU’s Filters – Reference is made to checking filters, but no detail given on what parameter to
indicate when a filter is required to be changed. Pressure drop is appropriate on central units.
5.
Packaged chillers –Reference is made to check settings, no detail as to what the appropriate
setting might be for condenser and evaporator, nor how to determine these or where to get this information. This leads to over safe settings being maintained leading to considerable additional use of electrical power. COP should be assessed, and at the very least the actual cooling load on the chiller to be assessed and recorded. It is proposed that the condenser pressure (temperature) be set to ensure that this delivers temperatures no greater than eight degrees above expected ambient temperatures. Similarly the evaporator temperatures should be in the range of the delivered cooled medium temperature
6.
For motors on fans it says to check operation and record amps. What is done with this data?,
what is acceptable level? For air and air off-takes for temperature assessment – what is acceptable and what is excessive? This ties into possible fin cleaning and approach temperature evaluation.
7.
For split ACU’s there is no mention as to assessing the appropriate use – eg control units locked
to cooling mode only in summer and heating mode only in winter.
8.
For Fans it mentions checking belts for looseness, but no mention of assessing the pulleys for
signs of wear leading to belt slippage.
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9.
For LPHW boiler no mention is made as to appropriate settings for operation. Focus on carrying
out combustion test – what is acceptable to pass (eg no CO present – may be 10% excess oxygen and pass). No assessment of efficiency of operation.
10.
For radiators it mentions to check the operation of all radiator valves. Consider adding that if
these require changing for any reason to replace with thermostatic operating valves.
11.
Consider addition to the chiller plant/ AHU section to assess the correct air flow through
equipment racks to maximise cooling impact.
12.
Consider the addition of a check to ensure that no unnecessary equipment is installed in data
centre – unnecessary equipment removed as appropriate.
13.
Consider addition of a paragraph to all procedures to request any identified opportunities for
energy reduction or improved maintenance to be forwarded with the completed maintenance report.
In reality the service specification details only address maintenance and not operations. This should be addressed.
5.5. Potential savings to be achieved from the changes in operational and maintenance practices Given the assessment of HVAC and directly connected data equipment loads being essentially base line and the fact that savings expected to be achieved are due to an accumulation of small savings as opposed to single large savings. It is proposed that for building B a savings target of 7% is set, with the majority of this to be saved with small changes such as condenser and evaporator set points, reduction of storage heater charge time, improvement of air flow through the date equipment racks and subsequent adjustment in room set point for chilled air and elimination of heating and cooling in spaces not in use.
6. Recommended methodology to assess impact of changes made As the energy savings in both sample sites are expected to yield savings from an accumulation of energy savings, it makes sense to use whole metered data to assess the impacts of change. This type of assessment is open to incorrect assessment and we shall address the issues relating to each here. 20
6.1. Site A With Building A it is expected that there is potential for significant energy savings in the region of 15% . It is difficult to put an exact saving on this due to limited detailed meter data to individual users but considering the chiller set points seen and in particular the relatively constant electrical consumption winter and summer it is believed that this figure is realistic.
To assess the savings in electricity made by implementation of the report recommendations will rely on electrical monitoring utilising whole metering also. It is recommended in this case that we will rely on comparisons to average weekly figures to give a basis for assessment.
The reason that this approach is recommended is because the potential savings are in the region of 15% and larger and we do not have enough data gathered pre implementation to allow more performance based assessments to be made. It should be possible to see after a period of six months that a stronger correlation of electrical consumption versus cooling degree days will be established and this should be to a base of 15.5 degrees. This will be a further indicator of successful implementation of savings. It is important however to take stock of all the potential variations that may impact on consumption in either a positive or negative manner and lead to errors in assessed data. The main independent variables are as follows: 1.
Hours of operation of the building in floor occupancy hours M2*hours
2.
Area set points for temperature.
3.
Number of occupants in the building
6.2. Site B Typically we would recommend that for verification of savings of energy projects whole facility metering would not be used to assess the impact of change where savings are not expected to exceed 15% of the total site consumption. It is however the case that for this particular facility there is a relatively strong energy to weather relationship and a high base load, with the overall consumption variation being small. (average of 2.6% variation in the absolute error between the true consumption and the expected consumption when this is normalised and takes into account the weather impacts).
It is important however to take stock of all the potential variations that may impact on consumption in either a positive or negative manner and lead to errors in assessed data. The main independent variables are as follows:
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1.
Weather – here we have taken into account the weather using the established prediction that
kWh = 45.866HDD (base 15.5) + 2592.9 2.
Number of hours that the call centres are in operation per day
3.
Use of call centres at night
4.
Area utilised in the building
5.
Area set points for temperature
It is recommended that the assessment be made utilising the 15 minute data available for the site, assessed once per month, but normalised for 28 days in the month. (use the first 28 days in the month only to ensure same number of weekdays and weekends per month assessed). Assess the actual usage against expected where the actual value of degree days seen in the month is fed into the equation. (Degree days can be got from www.degreedays.net) Ensure also that the correct numbers of days are used also for degree day assessment.
Improvements should be reported in % terms positive and negative each month and the average savings totalled every period.
7. Conclusion The conclusion that can be drawn from this assessment is that despite these buildings being well maintained and reliable, that there is considerable savings to be made in the operational and maintenance programs of the building without the need to invest monies in new technologies and equipment.
Some technical knowledge and understanding of your own plant and equipment is
desirable, but considerable knowledge can be gained from the commercial building O&M document to assist a user in identifying potential.
This report focuses on practical improvements as opposed to large technical improvements and there will always be further opportunities to be taken.
A good starting point in all cases is the review of your own energy data in whatever form available and assessment against those factors that you might expect to have an impact upon consumption. Because a relationship might not exist does not mean it should not exist and I would always make the comment that you can’t manage what you don’t understand, measurement is the easy part. Areas where the value of the potential savings are difficult to assess may require additional metering but in most commercial buildings the metering available is limited and reviewing consumption against factors overall can give some indication as to what is and not happening as expected.
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The Commercial building O&M document is an important aid to assessing potential for O&M improvements and whilst not all parts of the document are relevant to all building and care needs to be taken as to the level of detail required in operation and maintenance where the availability and time of technical staff is limited, the use of the document can aid a building owner to make savings without investments in areas otherwise overlooked.
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