12. Hot Water Production, A Tunisian geothermal case studyGEOTHERMALWater 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
13. Combined heating Systems
14. Steam Production and Utilization : Understanding steamThe diagram below helps to explain the various principles involved in thethermodynamics of steam. It shows the relationship between temperature andenthalpy (energy or heat content) of water as it passes through its phasechange.The reference point for enthalpy of water and steam is 0°C, at which point anenthalpy value of 0 kJ/kg is given to it (but of course water at 0°C has alot ofenergy in it, which is given up as it freezes - its not until 0K, absolute zero, whenit truely has no enthalpy!).As we increase the temperature of water, its enthalpy increases by 4.18 kJ/kg °Cuntil we hit its boiling point (which is a function of its pressure - the boiling pointof water is 100 °C ONLY at 1 atm. pressure). At this point, a large input ofenthalpy causes no temperature change but a phase change, latent heat is addedand steam is produced. Once all the water has vaporized, the temperature againincreases with the addition of heat (sensible heat of the vapour).
15. Steam Production and DistributionSteam is produced in large tube and chest heat exchangers, called water tube boilers ifthe water is in the tubes, surrounded by the flame, or fire tube boilers if the oppositeis true. The pressure inside a boiler is usually high, 300-800 kPa. The steamtemperature is a function of this pressure. The steam, usually saturated or of very highquality, is then distributed to the heat exchanger where it is to be used, and it providesheat 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 reducingvalve, 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 heatexchanger) and then the condensate (hot water) is returned to the boiler so it can bereused. The following image is a schematic of a steam production and distributioncycle.
16. Steam Production and Utilization
17. CogenerationPrincipals and case studies
18. Cogeneration (also combined heat and power, CHP) is the use of a heatengine or a power station to simultaneously generate both electricity anduseful heat. It is one of the most common forms of energy recycling.Conventional power plants emit the heat created as a by-product of electricitygeneration into the natural environment through cooling towers, flue gas, orby other means. By contrast CHP captures the by-product heat for domestic orindustrial heating purposes, either very close to the plant, or—especially inScandinavia and eastern Europe—as hot water for district heating withtemperatures ranging from approximately 80 to 130 °C. This is also calledCombined Heat and Power District Heating or CHPDH. Small CHP plants arean example of decentralized energy.In the United States, Con Edison distributes 30 billion pounds of 180 °Csteam each year through its seven cogeneration plants to 100,000 buildings inManhattan—the biggest steam district in the world. The peak delivery is 10million pounds per hour (corresponding to approx. 2.5 GW) This steamdistribution system is the reason for the steaming manholes often seen in"gritty" New York movies.
19. Other major cogeneration companies in the U.S. includeRecycled 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 berejected as waste heat, but in cogeneration this thermal energy is put to good use.
20. 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)
21. 2/ Présentation de la cogénération CRITERIA CHOICE TECHNICALS ECONOMICS ● INVESTISSEMENT EFFECIENCY SECURITY ● COST REDUCTIONRENOVATION
22. INVESTISSEMENT RISK TECHNICAL FINANCALDESIGN GAIN RELATED TO THEWARRANTY REPORTMAINTENANCE QUALITY ELEC/GAS COSTS
23. LA PRODUCTION COMBINEE MECANICAL THERMAL ENERGIE ENERGY PRODUCTION OF A FLUIDMACHINES HEAT TRANSFERAlternators AirCompressors SteamFans HEATED Water
24. 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.
25. Cogeneration, case studies Tunisian ceramic industries
26. Annual energy situationELEC 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
27. Gas Turbine Taurus T60 CERAMICS INDUSTRY IN TUNISIA Turbine Compressor Gearbox
28. Exhaust air duct
29. Heat used for production unit
30. Energy efficiency measures and evaluation of Energy savings
31. •Combustion contrôle•Boiler performance and management•Exchange losses contrôle•Distribution losses•Process losses•Facilities performance•Automatic control•Human use
32. Examples : house holders, same actions can be used for others•Insulate Your Existing Water Heater. If your electric water heater was installedbefore 2004, installing an insulating jacket is one of the most effective do-it-yourselfenergy-saving projects, especially if your water heater is in an unheated space. Theinsulating jacket will reduce standby heat loss—heat lost through the walls of thetank—by 25–40%, saving 4–9% on your water heating bills. Water heater insulationjackets are widely available for around $10. Always follow directions carefully wheninstalling an insulation jacket.• Insulate Hot Water Pipes. Insulating your hot water pipes will reduce losses as thehot water is flowing to your faucet and, more importantly, it will reduce standby losseswhen the tap is turned off and then back on within an hour or so. A great deal ofenergy and water is wasted waiting for the hot water to reach the tap. Even whenpipes are insulated, the water in the pipes will eventually cool, but it stays warmermuch longer than it would if the pipes weren’t insulated.• Lower the Water Heater Temperature. Keep your water heater thermostat set atthe lowest temperature that provides you with sufficient hot water. For mosthouseholds, 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 yourwater heating costs. When you are going away on vacation, you can turn thethermostat down to the lowest possible setting, or turn the water heater off altogetherfor additional savings.
33. Minimize Operating CostsEven if you aren’t going to buy a new water heater, you cansave a lot of energy and money with your existing systemby following a few simple suggestions.•Conserve Water. Your biggest opportunity for savings is to use lesshot water. In addition to saving energy (and money), cutting down onhot water use helps conserve dwindling water supplies, which in someparts of the country is a critical problem. A family of four each showeringfive minutes a day can use about 3500 litters per week—a three-yeardrinking water supply for one person! Water-conserving showerheadsand faucet aerators can cut hot water use in half. That family of four cansave 70 000 litters of water a year and the energy required to heat it.
34. InsulationInsulation reduces the amount of heat entering throughceilings or walls, keeping rooms cooler in summer, whilehelping to keep warmth inside your home in winter. Homeinsulation is designed to increase your comfort levels andminimize the use and running cost of cooling and heatingappliances, thereby also reducing greenhouse gas emissions.Correctly installed insulation in the ceiling can make a bigdifference in the size and operating times of the airconditioning unit you need.How much insulation is required and the type of insulationdepends on the climatic region you live in and the design ofyour home.
35. When choosing insulation, the most important factor to consider isits ‘R’ value. This is the measurement of a material’s resistance toheat flow and therefore its performance. The higher the ‘R’ value,the greater the resistance to heat transfer and the greater the energysavings. In some cases products with a different ‘R’ value willprovide similar insulation performance.Properly installed insulation to a recommended ‘R’ value isbelieved to lower ambient room temperatures by approximately2°C. Ceiling insulation with an ‘R’ value of 2.5 can reduce up to30 per cent of heat from entering your home in summer and keepgenerated heat inside during winter.
36. Evaluating Energy SavingThe problem of consumers in evaluating energy savinginvestments suggests the need for a uniform disclosure method.Disclosure for energy conservation is related to the use ofdisclosure policies in Truth-in-Lending and other areas. Fivemethods of evaluating energy saving investments are analyzed:the apparent payback method, the present value method, theactual payback method, the loan payment method, and the rateof return method. The rate of return method is the only methodthat is both easy to understand and valid. The probablelimitations in consumer understanding and use of informationrelated to energy conservation, however, make it likely that acombination policy of disclosure, education, and productstandards would be the most effective alternative for reachingenergy conservation goals.
37. 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 dutilisat incande TempsLOCAUX 36 w 18 w 60 w 25 w r an ANCE GIE T cence installer bre e installer ement energ dinars ion sc retourCouloirtech 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 0,6Chambres 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 0,9Lavevaiss 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 0,9Rest à lacarte 27 24 3 365 2,220 2430 136 2430,9 11 51 2,22 0,561 714 1817 98,097 7,3 67,014 4,3Toil.Rest 10 6 365 0,600 1314 73,6 1314 11 10 0,6 0,11 140 1073 57,947 3,7 26,280 1,7Restaurant 108 38 10 365 6,168 2251 1260 8322 11 38 2,28 0,418 532 6796 367,000 2,2 166,440 1,0Bar.Palmiers 24 61 7 365 4,524 1155 647 9351,3 11 61 3,66 0,671 854 7637 412,392 3,1 187,026 1,4CouloirRecep 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
38. Example: Energy Saving Potentials for Gas Fired Industrial FurnacesEnergy efficiency has become a top priority for many companies in thesteel and heat treating business. Since hot exhaust gases represent thelargest source for losses in most industrial furnaces, preheating thecombustion air provides the highest potential for energy savings.A new type of regenerative burner for radiant tube heating will also bepresented.Regenerative air preheating is accepted as the most effective way toincrease energyefficiency for high temperature process heating but was seen in the pastas to complex and expensive for heating small and medium size heattreating furnaces.
39. Energy Efficiency related to flue gas lossesEfficiency is usually defined as:efficiency = (benefit) /(expenditure)Regarding firing systems for industrial furnaces, efficiency oravailable 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, orprocess temperature. For asystem without air preheat, it becomes obvious that theefficiency is vanishing with risingexhaust gas temperature. At a 1000°C process temperature, atleast 50% of the fuel input willbe lost as hot exhaust gas heat.Figure 1:
40. To determine the usefullness of air preheat, the relative air preheat ecan be defined as:e =(J preheat – J air)/(J exhaust – J air) # J preheat / J exhaustwith: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 theburner. Energy losse between a central heat exchanger and the burnerhave to be considered. The hot exhaust temperature is the temperatureof the exhaust gases leaving the furnace. In most cases thistemperature is close to the process temperature. In radiant tube heatedfurnaces this temperature can be substantially higher than the furnacetemperature. The air inlet temperature is usually ambiant air andtherefore the relative air preheat can be expressed at the ratio ofpreheat temperature to hot exhaust temperature. The relative airpreheat is a good figure to characterize a heat exchanger for airpreheating.
41. savingsThe savings can be calculated as:savings =1 – (low efficiency / high efficiency)That translates to savings of 20% if a system with 68% efficiency isupgraded to 85% efficiency.Continous direct fired furnaces