Energy Audit in Building A Regional Training Workshop 1 - 5 June, 2010

1. ENERGY AUDITING OF
HEATING AND WATER
HEATING SYSTEMS
Abdelhak Khemiri, Phd.
June, 2010

2. •Heating systems
•Boilers efficiency
•Water heating systems
•Cogeneration
•Energy efficiency measures and evaluation
of Energy savings

3. Heating systems
Heat Production and Hot water
production

5. Burner components and combustion efficiency
Legend :1. engine, 2. control, box
3. transformer, 4. ectrodes, 5. fan, 6. volute, 7. deflector, 8. Jet,
9. heater, 10. photosensitive cell , 11. solenoid valve,
, 12. pump and a pressure regulator

6. Total Combustion
Real Combustion (air access)

7. Combustion Diagramm
Air reduction Surplus Air
Gas Losses
Carbon Dioxide (CO2)
Combustible
Mixed Air
Oxygene (O2)
Carbon Monoxyde
(CO)
Surplus Air

8. H2S
NOX HCN
NO + NO2 HCl
HF
H2O NH3
O2 SO2
CO Poussière
Suie
CO2
CXHY
C total

9. Heat Losses

10. Efficiency and losses, tunisian case study
70%
60%
50%
40%
30%
20% Rendement
10%
Log. (Rendement)
0%
957 1080 1093 1330 1630 1834 2117 2799 2834 2912 2938 2997
BECS [m3]

11. Hot water losses, tunisian hotel case study
250
Σpertes/VECS ΣpertesFixes
200 Logarithmique (Σpertes/VECS) Linéaire (ΣpertesFixes)
150
100
50
0
11
30
30
31
32
33
35
36
38
39
42
43
44
46
49
52
57
59
62
64
68
71
73
77
79
83
86
88
89
91
92
93
95
98
101
108
Becs [m3]

12. Energy losses, case study

13. Hot Water Production, A Tunisian geothermal case study
GEOTHERMAL
Water
Hot Water loop From rooms
52° H Water to Rooms Hot Water loop
48° Hot Water to
Kitchen From Kitchen
TUBE TEMOIN
25° TUBE Sample
Exchanger
15°
5000 L 5000 L 5000 L
Cold water
Exchanger
BOILERS

14. Combined heating Systems

15. Steam Production and Utilization : Understanding steam
The diagram below helps to explain the various principles involved in the
thermodynamics of steam. It shows the relationship between temperature and
enthalpy (energy or heat content) of water as it passes through its phase
change.
The reference point for enthalpy of water and steam is 0°C, at which point an
enthalpy value of 0 kJ/kg is given to it (but of course water at 0°C has alot of
energy in it, which is given up as it freezes - it's not until 0K, absolute zero, when
it truely has no enthalpy!).
As we increase the temperature of water, its enthalpy increases by 4.18 kJ/kg °C
until we hit its boiling point (which is a function of its pressure - the boiling point
of water is 100 °C ONLY at 1 atm. pressure). At this point, a large input of
enthalpy causes no temperature change but a phase change, latent heat is added
and steam is produced. Once all the water has vaporized, the temperature again
increases with the addition of heat (sensible heat of the vapour).

17. Steam Production and Distribution
Steam is produced in large tube and chest heat exchangers, called water tube boilers if
the water is in the tubes, surrounded by the flame, or fire tube boilers if the opposite
is true. The pressure inside a boiler is usually high, 300-800 kPa. The steam
temperature is a function of this pressure. The steam, usually saturated or of very high
quality, is then distributed to the heat exchanger where it is to be used, and it provides
heat by condensing back to water (called condensate) and giving up its latent heat.
The temperature desired at the heat exchanger can be adjusted by a pressure reducing
valve, which lowers the pressure to that corresponding to the desired temperature.
After the steam condenses in the heat exchanger, it passes through a steam trap
(which only allows water to pass through and hence holds the steam in the heat
exchanger) and then the condensate (hot water) is returned to the boiler so it can be
reused. The following image is a schematic of a steam production and distribution
cycle.

18. Steam Production and Utilization

21. Cogeneration
Principals and case studies

22. Cogeneration (also combined heat and power, CHP) is the use of a heat
engine or a power station to simultaneously generate both electricity and
useful heat. It is one of the most common forms of energy recycling.
Conventional power plants emit the heat created as a by-product of electricity
generation into the natural environment through cooling towers, flue gas, or
by other means. By contrast CHP captures the by-product heat for domestic or
industrial heating purposes, either very close to the plant, or—especially in
Scandinavia and eastern Europe—as hot water for district heating with
temperatures ranging from approximately 80 to 130 °C. This is also called
Combined Heat and Power District Heating or CHPDH. Small CHP plants are
an example of decentralized energy.
In the United States, Con Edison distributes 30 billion pounds of 180 °C
steam each year through its seven cogeneration plants to 100,000 buildings in
Manhattan—the biggest steam district in the world. The peak delivery is 10
million pounds per hour (corresponding to approx. 2.5 GW) This steam
distribution system is the reason for the steaming manholes often seen in
"gritty" New York movies.

23. Other major cogeneration companies in the U.S. include
Recycled Energy Development and leading advocates include
Tom Casten and Amory Lovins.
By-product heat at moderate temperatures (100-180°C) can
also be used in absorption chillers for cooling. A plant
producing electricity, heat and cold is sometimes called
trigeneration or more generally: polygeneration plant.
Cogeneration is a thermodynamically efficient use of fuel. In
separate production of electricity some energy must be
rejected as waste heat, but in cogeneration this thermal energy
is put to good use.

24. 1/ Présentation de la cogénération
COMBINED PRODUCTION ELECTRICITY +
COGENERATION IS A N IPP HEAT (MAX 20 MWH)
COGENERATION
GAINS
(ENERGY + FINANCE) POLLUTION REDUCTION
COGENERATION IN EUROPE >>>>>>>>> PRODUCTION 17 % OF
ELECTRICAL ENERGY (2004)

25. 2/ Présentation de la cogénération
CRITERIA
CHOICE
TECHNICALS ECONOMICS
● INVESTISSEMENT
EFFECIENCY
SECURITY ● COST REDUCTION
RENOVATION

26. INVESTISSEMENT RISK
TECHNICAL FINANCAL
DESIGN GAIN RELATED TO THE
WARRANTY REPORT
MAINTENANCE QUALITY ELEC/GAS COSTS

27. LA PRODUCTION
COMBINEE
MECANICAL THERMAL
ENERGIE ENERGY
PRODUCTION OF A FLUID
MACHINES HEAT TRANSFER
Alternators Air
Compressors Steam
Fans HEATED Water

32. Legal framework of the electrical production
LAWS AND DECISIONS ON THE COGENERATION
• Installation of CHP is assessed based on the
following quality criteria:
• -Annual overall performance:
• RG = (C + E) /Q
• -Ratio of recovery:
• RR = C/E
• -Effective use of thermal energy produced.

33. Cogeneration, case studies
Tunisian ceramic industries

35. Annual energy situation
ELEC
turbine Production : 39 684 489 kWh
Consumption :
Turbine: 25 762 128 kWh
From STEG: 481 166 kWh
turbine Production is :
Consumed in factory: 25 762 128 kWh
To STEG: 13 922 361 kWh
Electrical Energy consumption 2% Electrical repartition
35%
65%
98% Consommée par la STEG
Provenance turbine

36. Gas Turbine Taurus T60 CERAMICS INDUSTRY IN TUNISIA
Turbine Compressor Gearbox

37. Exhaust air duct

38. Heat used for production unit

39. Energy efficiency measures and
evaluation of Energy savings

40. •Combustion contrôle
•Boiler performance and management
•Exchange losses contrôle
•Distribution losses
•Process losses
•Facilities performance
•Automatic control
•Human use

41. Examples : house holders, same actions can be used for others
•Insulate Your Existing Water Heater. If your electric water heater was installed
before 2004, installing an insulating jacket is one of the most effective do-it-yourself
energy-saving projects, especially if your water heater is in an unheated space. The
insulating jacket will reduce standby heat loss—heat lost through the walls of the
tank—by 25–40%, saving 4–9% on your water heating bills. Water heater insulation
jackets are widely available for around $10. Always follow directions carefully when
installing an insulation jacket.
• Insulate Hot Water Pipes. Insulating your hot water pipes will reduce losses as the
hot water is flowing to your faucet and, more importantly, it will reduce standby losses
when the tap is turned off and then back on within an hour or so. A great deal of
energy and water is wasted waiting for the hot water to reach the tap. Even when
pipes are insulated, the water in the pipes will eventually cool, but it stays warmer
much longer than it would if the pipes weren’t insulated.
• Lower the Water Heater Temperature. Keep your water heater thermostat set at
the lowest temperature that provides you with sufficient hot water. For most
households, 120°F water is fine (about midway between the “low” and “medium”
setting). Each 10°F reduction in water temperature will generally save 3–5% on your
water heating costs. When you are going away on vacation, you can turn the
thermostat down to the lowest possible setting, or turn the water heater off altogether
for additional savings.

42. Minimize Operating Costs
Even if you aren’t going to buy a new water heater, you can
save a lot of energy and money with your existing system
by following a few simple suggestions.
•Conserve Water. Your biggest opportunity for savings is to use less
hot water. In addition to saving energy (and money), cutting down on
hot water use helps conserve dwindling water supplies, which in some
parts of the country is a critical problem. A family of four each showering
five minutes a day can use about 3500 litters per week—a three-year
drinking water supply for one person! Water-conserving showerheads
and faucet aerators can cut hot water use in half. That family of four can
save 70 000 litters of water a year and the energy required to heat it.

43. Insulation
Insulation reduces the amount of heat entering through
ceilings or walls, keeping rooms cooler in summer, while
helping to keep warmth inside your home in winter. Home
insulation is designed to increase your comfort levels and
minimize the use and running cost of cooling and heating
appliances, thereby also reducing greenhouse gas emissions.
Correctly installed insulation in the ceiling can make a big
difference in the size and operating times of the air
conditioning unit you need.
How much insulation is required and the type of insulation
depends on the climatic region you live in and the design of
your home.

44. When choosing insulation, the most important factor to consider is
its ‘R’ value. This is the measurement of a material’s resistance to
heat flow and therefore its performance. The higher the ‘R’ value,
the greater the resistance to heat transfer and the greater the energy
savings. In some cases products with a different ‘R’ value will
provide similar insulation performance.
Properly installed insulation to a recommended ‘R’ value is
believed to lower ambient room temperatures by approximately
2°C. Ceiling insulation with an ‘R’ value of 2.5 can reduce up to
30 per cent of heat from entering your home in summer and keep
generated heat inside during winter.

45. Evaluating Energy Saving
The problem of consumers in evaluating energy saving
investments suggests the need for a uniform disclosure method.
Disclosure for energy conservation is related to the use of
disclosure policies in Truth-in-Lending and other areas. Five
methods of evaluating energy saving investments are analyzed:
the apparent payback method, the present value method, the
actual payback method, the loan payment method, and the rate
of return method. The rate of return method is the only method
that is both easy to understand and valid. The probable
limitations in consumer understanding and use of information
related to energy conservation, however, make it likely that a
combination policy of disclosure, education, and product
standards would be the most effective alternative for reaching
energy conservation goals.

46. The pay buck mothod , Tunsian study case
Pb = Investment / ∑ gains
puissanc Puissanc
Energie e lampes e durée frais
T.N T.N L L H/Jou Jour/ PUISS ENER COU incandes a Nom substitué P à investiss gain gain d'utilisat incande Temps
LOCAUX 36 w 18 w 60 w 25 w r an ANCE GIE T cence installer bre e installer ement energ dinars ion sc retour
Couloir
tech 1 3 3 16 365 0,234 1366 76,5 1051,2 11 3 0,18 0,033 42 858 46,358 1,4 21,024 0,6
Chambres Froi 1 5 11 365 0,318 1276 71,5 1204,5 11 5 0,3 0,055 70 984 53,118 2,0 24,090 0,9
Lave
vaiss 1 5 11 365 0,318 1276 71,5 1204,5 11 5 0,3 0,055 70 984 53,118 2,0 24,090 0,9
Rest à la
carte 27 24 3 365 2,220 2430 136 2430,9 11 51 2,22 0,561 714 1817 98,097 7,3 67,014 4,3
Toil.Rest 10 6 365 0,600 1314 73,6 1314 11 10 0,6 0,11 140 1073 57,947 3,7 26,280 1,7
Restauran
t 108 38 10 365 6,168 2251 1260 8322 11 38 2,28 0,418 532 6796 367,000 2,2 166,440 1,0
Bar.Palmi
ers 24 61 7 365 4,524 1155 647 9351,3 11 61 3,66 0,671 854 7637 412,392 3,1 187,026 1,4
Couloir
Recep 24 3 14 330 1,515 6999 392, 6999,3 11 27 1,515 0,297 378 5627 303,867 1,7 149,688 0,8

47. Example: Energy Saving Potentials for Gas Fired Industrial
Furnaces
Energy efficiency has become a top priority for many companies in the
steel and heat treating business. Since hot exhaust gases represent the
largest source for losses in most industrial furnaces, preheating the
combustion air provides the highest potential for energy savings.
A new type of regenerative burner for radiant tube heating will also be
presented.
Regenerative air preheating is accepted as the most effective way to
increase energy
efficiency for high temperature process heating but was seen in the past
as to complex and expensive for heating small and medium size heat
treating furnaces.

48. Energy Efficiency related to flue gas losses
Efficiency is usually defined as:
efficiency = (benefit) /(expenditure)
Regarding firing systems for industrial furnaces, efficiency or
available heat is defined as:
efficiency = (fuel input - exhaust gas losses)/fuel input =
1 - fuel input - exhaust gas losses)/(fuel input)
Figure 1 shows the efficiency as a function of exhaust gas, or
process temperature. For a
system without air preheat, it becomes obvious that the
efficiency is vanishing with rising
exhaust gas temperature. At a 1000°C process temperature, at
least 50% of the fuel input will
be lost as hot exhaust gas heat.
Figure 1:

50. To determine the usefullness of air preheat, the relative air preheat e
can be defined as:
e =(J preheat – J air)/(J exhaust – J air) # J preheat / J exhaust
with:
J preheat air preheat temperature [°C]
J exhaust hot exhaust temperature [°C]
Jair air inlet temperature [°C]
The air preheat temperature is the temperature which is supplied to the
burner. Energy losse between a central heat exchanger and the burner
have to be considered. The hot exhaust temperature is the temperature
of the exhaust gases leaving the furnace. In most cases this
temperature is close to the process temperature. In radiant tube heated
furnaces this temperature can be substantially higher than the furnace
temperature. The air inlet temperature is usually ambiant air and
therefore the relative air preheat can be expressed at the ratio of
preheat temperature to hot exhaust temperature. The relative air
preheat is a good figure to characterize a heat exchanger for air
preheating.

51. savings
The savings can be calculated as:
savings =1 – (low efficiency / high efficiency)
That translates to savings of 20% if a system with 68% efficiency is
upgraded to 85% efficiency.
Continous direct fired furnaces

52. Continous furnace with central
recuperator