Idea 1
Proposal for reclaiming heat from Compressors.
It is possible to extract, by heat transfer, as much as 80-90% of the energy that the electric motor placed
into the compressed air
Our compressors run approximately 6000 hours a year1
180 kW motor on Atlas Copco compressor
assuming our compressors running approximately 6000 hours
assuming a minimum 80% of heat can be reclaimed
Table1 Source: Carbon trust
Savings based on replacement of gas heating with a boiler efficiency of 85% and a gas cost of 2.5p/kWh
if heat is used to save on electrical use it may offer greater savings depending on costs of power.
Taking a mean figure of the motor rating associated with a 160kW and 200 kW would give
an average of 180kW. Taking a mean of the costs associated with these motors gives an annual saving
potential average of £8470.5. Given our compressors run for around 6000 hours it gives a potential
saving of £25,411.5 and if 3 compressors are running this potential could be £76,234.5
If more than 80% can be reclaimed savings potential is greater still.
1
Based on 24hrs/day x 5 days/week 50 weeks/year
Suggest configeration to transfer heat directly from compressors
A similar set up in figure 3 could be used to supply hot water for radiators, washing facilities
and if a suitable heat exchanger is used drinking water.
If the yards continue to adopt localised compressors then similar heat salvaging techniques
could be adopted all over the site to reduce local heating costs and energy consumption. Heat
exchangers could also be connected up to hot water returns to pre-heat water and reduce boiler
house running costs. (Check with plumber to see if this is feasible)
Costs: There may be costs associated with purchasing ducting, dampers, heat exchangers and
additional pipework however depending on energy consumption, these costs may be offset by
the savings made in the first year.
Researched by David Ewing, Maintenance Engineer originally in October 2015 , reviewed and
modified April 2016
Idea 2
Increase energy efficiency of Maintenance workshop/work shop office
HEATING
Maintenance workshop office is heated by a 2kW electric heater. During autumn/winter/spring
months it is left on almost 24/7 due to rapid heat loss within office, it also often is turned on
occasionally in summer as office gets no natural heating from sunlight.
Assuming there it runs for 5000 hours out of 8760 hours annually (60% of the year)
5000 x 2kW= approximately 10,000kWh used per year on this heater alone. Assuming approx.
14.0p/kWh this would represent potential annual costs up to £1,400 per year.
I would propose improving the energy efficiency of the office by insulating the outer wall. The
values below show the difference in thermal conductivity in an uninsulated wall and an
insulated wall
Material & Layer
Internal Brick
External Brick
Current non-insulated wall
Thickness(mm)
Conductivity)W/mK)
Resistance(M2K/W
100
0.62
0.16
100
0.84
0.12
Total Resistance
0.46
U Value
Material & Layer
Outer Brick
Inner Brick
Rockwool
Plywood
2.17 W/M2K
Thickness
Total Resistance
U-Value
Insulated Wall
Conductivity
100
100
100
100
Resistance
0.62
0.84
0.04
0.14
0.16
0.12
2.5
0.09
3.05
0.33 W/m2K
The U-value is potentially higher as a large section of the wall is just plywood and glass which
has poor resistance to thermal conductivity. This potentially allows doubling up of insulation
over a large section of the wall which could further reduce the U-Value in ¾ of the wall to
around 0.18W/m2K.
This means 0.18 Watts of energy per metre square is lost per degree of temperature difference
as opposed to 2.17 over an uninsulated wall.
Combined with lowering the ceiling in the office area, sealing some cracks in the walls and
insulating a section of the door this potentially could mitigate a lot of heat loss within the office
space.
It would also improve the aesthetics of the office.
SCOPE OF WORK
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Disconnect electrical fittings from wall
Remove redundant fittings from office
Remove plywood currently on wall
Fill gaps in wall with caulk or expanding foam
Install batons on section of wall that is glass
Construct baton frame to mount onto wall
Insulate wall and frame
Sheet wall with plyboard and paint
Construct joists for new ceiling
Install suspended ceiling
Install new lighting
Insulation and cover section at office door
Reconnect all electrical fittings
Materials required
wall surface area is approximately 15m2 adding on 20% spare material for odd cuts
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Rockwool insulation 8 packs code 123326 (100mm x 600mm x 1,200)
Expanding foam 1 tin
Decorators caulk available from ship store
Wooden batons 10 off 4,000mm x 100mm x50mm
Paint suitable for office
Screws
LIGHTING
Within the office area there is also 2x58W strip lights. Currently these lights are
operating for 17 hours a day Monday-Thursday , 14 hours on a Friday and around 12
hours over weekends for an average total of 94 hours per week.
This represents 94Hours x 2(58Watts)= 10,904Wh per week which is 10.9kWh.
(This is likely to be higher as measuring the current in the system often runs at 0.5 amps
which at 240 V would be 120 Watts [Power=Current x Voltage])
Annual cost is 10.9kWh x 52 = 566kWh per year which represents an annual lighting
cost of £79
If a lower ceiling was to be fitted it could have LED lighting installed which although
more expensive to buy have a longer lifetime and lower running costs.
I have been informed we may have 4 LED lights left over from the COC refurbishment
which if used could mitigate the costs of purchashing new fittings.
If unavailable then potential replacements could be 2x36W LED panel lights which are
80W Fluorescent equivalents
representing 72Wh which operating at the same rate would be 363.6 kWh/year the
annual cost of running these fittings would be £50.90 representing a potential annual
energy saving of £30 or 64% of current lighting costs.
Installation costs
Cost to install lighting would be down to availability of spare lights or purchase costs of
new fittings as maintenance personnel could fit a quiet periods.
The 36Watt examples I suggested have a unit cost of £44 so two of these would cost £88
which would pay for itself after 3 years of operation. The rated lifetime of these lamps is
50,000hrs which should last 10 years under current usage.
Workshop lighting
Currently the maintenance workshop is lit by 60 5’ x 58W fluorescent tubes
Running for the same estimated time as the charge hands office lighting these lights use
approximately 17,010kWh/year which represents a cost of £2,381.4
Replacing these lights with 60 5’ x 24W LED tubes should essentially cut this energy use
down to 7,038kWh per year which would have a running cost of £985.4 per year or 41%
of previous consumption.
New LED tubes would cost approximately £960 to replace all the old lamps in the
workshop but this should see full cost recovery within the first year of use.
These lamps could also be fitted to the maintenance office if replacement fittings is not
progressed.
Similar LED lighting could also start to be rolled out across office environments within
the workplace. Purchasing a small batch to allow for testing and replacement of lamps as
required would spread costs over a longer period.
I think carrying out these operations in the maintenance workshop just now using
maintenance personal would allow the effectiveness to be judged and consider using
these standards when area above workshop is refurbished.