Low Carbon Conversion and Nuclear Power Energy Conservation and Management in Buildings Renewable Energy*NBSLM03E (2010) Low Carbon Technologies and Solutions: Sections 1 - 5N.K. Tovey () M.A, PhD, CEng, MICE, CEnv

Low Carbon Solutions may be achieved by:

Improving the overall energy efficiency in the production and distribution of energy. Using low carbon energy sources and conversion technologies. Using Nuclear PowerUsing Renewable Energy Improving end use conversion efficiency throughImproving appliance efficiency/technologyImproving insulation and related issues in buildings Enhancing Energy Management and analysisAwareness Raising

Low Carbon Technologies and Solutions*

Energy is consumed in extracting energy, processing it and delivering it.Primary Energy Ratio The Ratio of Energy as it exists in the ground to the energy delivered at point of final use (see NBSLM01E handout).

Improvements in Electricity Generation Efficiency can significantly reduce energy losses and carbon emissionsImproving the overall energy efficiency in the production and distribution of energy. *

FuelPrimary Energy RatioCoal1.0227Oil1.1292Gas1.062Electricity2.911

Different Fossil Fuels as a result of their chemical composition have a higher or lower proportion of their mass as carbon.Burning natural gas (mostly methane CH4 ) produces CO2 and water. Coal on the other hand is mostly carbon and produces most CO2 when burnt.Typical emission factors from the combustion of a fuel (Gross CV):

In electricity generation it is common to raise steam for the turbine. If this is done using gas then the carbon emissions will be only 183.58 / 310.05 = 59.2% of those emissions using the same technology and coal.Gas generation can exploit more efficient technologies resulting in further reduction.

*Using low carbon energy sources

FuelEmission factor gms/kWhFuelEmission factor gms/kWhNatural gas183.58Fuel Oil265.30LPG214.19Domestic Coal295.82Petrol239.76Industrial Coal307.94Diesel250.12Coal used for electricity generation310.05Burning oil245.55

*Section 2: Low Carbon Energy CONVERSION SolutionsFirst Law:W = Q1 - Q2so efficiency

But Carnot saw thatHeat TemperatureHeat EngineRevision from Module NBSLM01E: Generation of Work/ElectricityWe saw there was only limited scope for improving efficiency so long as we used steam as the primary fluid in electricity generation.What about Combined Cycle Gas turbines?

*Section 2: Low Carbon Energy CONVERSION SolutionsRevision from Module NBSLM01E: Heat PumpsHeat PumpsHeat PumpHeat Out Q1A Heat Pump is a reversed Heat Engine: NOT a reversed RefrigeratorCoefficients of Performance of 3 5 are possible. Significant savings are possible as a Heat Pump works with Thermodynamics not against it as in a Heat Engine.

Section 3: Combined Cycle Gas TurbinesAn open cycle gas turbine ~ A jet engineHigh T1 but also high T2 so efficiency is low ~ 23%

Section 3: Combined Cycle Gas TurbinesMultiple Shaft MachinesCondenser

*Practical Efficiencies:-Gas Turbine alone20 - 25%Steam Turbine alone35 - 38%CCGT 47 - 52%Combined Cycle Gas Turbine*Section 3: Combined Cycle Gas TurbinesMultiple Shaft Machines

Output from Gas Turbine: 0.23 units of power to generator and 0.77 units to WHB Generator is ~ 95% efficient so output ~ 0.22 units Waste Heat boiler is ~ 80% efficient so there will be ~ 0.15 units lost with 0.8*0.77=0.62 units effective for raising steam. Shaft power from Steam turbine = 0.62 * 0.486 = 0.30 units with 0.32 units to condenser Total electrical output = 0.22 + 0.28 = 0.50units of which 0.03 units are used on station Overall efficiency = 47%**ElectricityElectricityGas turbineT1 = 950oC = 1223 KT2 = 500oC = 823K

Isentropic efficiency ~ 80%Steam turbineT1 = 500oC = 773 KT2 = 30oC = 303K

Section 3: Combined Cycle Gas TurbinesMultiple Shaft Machines a worked example

Exhaust Gases < 100oCExhaust Gases 600oCSection 3: Combined Cycle Gas TurbinesSingle Shaft MachinesCondenser*

*Early CCGTs had multiple shafts with separate generators attached to gas turbinesSome had two or more gas turbines providing heat to waste heat boilers which powered a single steam turbineModern CCGTs tend to have a common shaft with a gas turbine and steam turbine turning a single generator.Advantages of single shaft machines: tend to have lower capital costTend to have higher overall efficiencies up to 55/56% - e.g. Great YarmouthDisavantages:No option to run gas turbine by itself Gas Turbines can reach full output in a matter of minutes.Steam turbines take 6 - 8 hours or moreGas Turbines tend to have higher NOx emissions and special provision is needed to reduce these levels e.g. injecting steam into gas turbine.

Section 3: Combined Cycle Gas Turbines

*Section 4: Combined Heat and Power*

*First Law of Thermodynamics: we can neither create or destroy energy ie Work out = Heat in Heat Out Second Law states we must always reject Heat and efficiency = If we could utilise all of rejected heat

The 1947 Act stated Electricity must be generated as efficiently as possible i.e. Work/Electricity (not energy) was King

Section 4: Applications of ThermodynamicsCombined Heat and Power (1)*

*Heat is normally rejected at ~ 30oC from a steam turbineToo low a temperature for useful space heating

Reject heat at 100oC

i.e. Less electricity is generated, but heat is now usefulTypically there are boiler and other losses before steam is raisedAssume only 80% of energy available in coal is available.And technical (isentropic efficiency) is 75%Then for 1 unit of coal - electricity generated case 1 = 0.8*0.75*0.639 = 0.38 units case 2 = 0.8*0.75*0.555 = 0.33 units + up to 0.47 units of heator up to 0.8 units in total. Typically 10% of heat is lost so 0.73 units available.Section 4: Applications of ThermodynamicsCombined Heat and Power (2)

*Back Pressure Steam TurbineITOC or Pass out Steam TurbineGas Turbine with CHP also Diesel/gas engine with CHPProblem:For most CHP plant, electrical output will be limited if there is no requirement for heat.

ITOC provides greater flexibilityAlthough capital cost is greaterSection 4: Combined Heat and Power (3)*

*ProcessIntegrated Electricity Generation, Process Heat, Space Heat and Air compression at ICI Wallerscote Plant in late 1970sSection 4: Combined Heat and Power (4)

*GeneratorGeneratorSteam TurbineGas TurbineFuel in 239 MWGT Temp 1127oC Heat Lost 24 MWUseful Heat 98 MWElectricity 55 MWElectricity 62 MWSection 4: CCGT with CHP

*Unless there is an industrial heat load, CHP plant capacity should be based on an approximate summer time heat load with supplementary heating provided by normal boilers in coldest months of year.Section 4: Combined Heat and Power Example of a Small Scale Scheme (1)

Chart1

84009200

84006600

84002100

7500Apr

5500May

4000Jun

4000Jul

4000Aug

6500Sep

8400100

84002100

84007000

Heat from CHP

Supplementary Heat

kW

Heat Supply

Sheet1

MonthTemp.Space Heat Demand (kW)Total Heat Demand (kW)Electricity (kW)CHP Heat available (kw)Useful CHP Heat (kW)Supplementary Heat Needed (kW)actual electricity that can be generatedSupplementary Electricity Needed

[1][2][3][4][5][6][7][8] = [4] [7][9][10]

Heat from CHPHeat from CHPSupplementary Heat

Jan1.91360017600780084008400920060001800

Feb4.51100015000720084008400660060001200

Mar965001050068008400840021006000800

Apr12350075006250840075005357***893

May14150055005800812055003929***1871

Jun16040005200728040002857***2343

Jul17040004800672040002857***1943

Aug16040004800672040002857***1943

Sep13250065005200728065004643***557

Oct11450085006200840084001006000200

Nov965001050068008400840021006000800

Dec4.11140015400780084008400700060001800

GWhGWhGWhGWhGWhGWhGWh

TOTALS78.4853.7568.3458.9719.5142.1211.63

Imported ElectricityCHP electricity

Jan18006000

Feb12006000

Mar8006000

Apr8935357

May18713929

Jun23432857

Jul19432857

Aug19432857

Sep5574643

Oct2006000

Nov8006000

Dec18006000

Sheet1

Heat from CHP

Supplementary Heat

kW

Sheet2

Imported Electricity

CHP electricity

kW

Sheet3

*Hot water and process heat demand is constant over the year at 4000 kWHeat loss rate for buildings is 1000 kW oC-1Existing Heating provided by gas (80% efficiency).Mean space heat demand in January= (15.5 1.9) * 1000 = 13 600 kWThis is the balance temperature we shall discuss this in section 11.. Section 4: Example of a Small Scale CHP Scheme (2)

A CHP scheme in a large building complex e.g. a University/Hospital has installed 6000 kW of CHP electrical generation capacity.

This is supplemented by supplementary boilers for peak winter heat demand.

The actual electricity demands are shown. Note in some months these are greater than the installed capacity

MonthMean Temperature (oC)mean Electricity Demand (kW)11.9780024.57200396800412625051458006165200717480081648009135200101162001196800124.17800

*

Column [4] values

= col[3] + 4000

The 4000 is hot water and process heat requirement.

Column 3 values

= (15.5 col [2])* 1000

15.5oC is the balance or neutral temperature at which no heating is required. Incidental gains from appliance heat and body heat increase temperature to comfort level.

Column [5] is electricity demand from Previous SheetColumn [6] indicates the potential amount of heat which would be available. Typically it is around 1.4 times the electricity generation so Col [6] = 1.4 * col [5] subject to a maximum electricity generation of 6000 kWi.e. when electrical demand > 6000kW, only 6000 * 1.4 = 8400 kW will be available for heat.

Col [7] is actual amount of heat that can be usefully used. i.e if col [6] is less than heat demandCol [7] = Col[6]If Col[6] is greater than heat demand then the useful amount = heat demand

Maximum generation = 6000 kW electricalSection 4: Example of a Small Scale CHP Scheme (3)

MonthTemp(oC)Space Heat Demand (kW)Total Heat Demand (kW)Electricity(kW)CHP Heat available (kW)Useful CHP Heat (kW)[1][2][3][4][5][6][7]Jan1.91360017600780084008400Feb4.51100015000720084008400Mar9650010500680084008400Apr1235007500625084007500May1415005500580081205500June1604000520072804000July1704000480067204000Aug1604000480067204000Sep1325006500520072806500Oct1145008500620084008400Nov9650010500680084008400Dec4.11140015400780084008400

*

Column [8] is supplementary heat required from back up boilers

Col [8] = col [4] col [7]

Column [9] is actual electricity that can be generated.If the heat demand is greater than 8400, then units can be run at full output i.e. 6000 kW.If heat requirement is less than 8400kW, then output of generators will be restricted to a maximum ofCol [7] / 1.4

The totals represent the total amount of heat or electricity generated or required over the year. Using 30 day months the totals in each column will be: mean values * 24 * 30

Column [10] is additional electricity needed.Note: highest import occurs when electricity demand is least.

Section 4: Example of a Small Scale CHP Scheme (4)

MonthTotal Heat Demand (kW)Electricity (kW)Useful CHP Heat (kW)Supple-mentary Heat (kW)actual electricity generatedSupplementary Electricity Needed[1][4][5][7][8][9][10]Jan1760078008400920060001800Feb1500072008400660060001200Mar105006800840021006000800April7500625075005357***893May5500580055003929***1871June4000520040002857***2343July4000480040002857***1943Aug4000480040002857***1943Sep6500520065004643***557Oct8500620084001006000200Nov105006800840021006000800Dec1540078008400700060001800GWhGWhGWhGWhGWhGWhTOTAL78.4853.7558.9719.5142.1211.63

* Electricity generation in summer is restricted and import is highest when demand is least*Section 4: Example of a Small Scale CHP Scheme (5)

Chart2

18006000

12006000

8006000

8935357

18713929

23432857

19432857

19432857

5574643

2006000

8006000

18006000

Imported Electricity

CHP electricity

kW

Electricity Supply

Sheet1

MonthTemp.Space Heat Demand (kW)Total Heat Demand (kW)Electricity (kW)CHP Heat available (kw)Useful CHP Heat (kW)Supplementary Heat Needed (kW)actual electricity that can be generatedSupplementary Electricity Needed

[1][2][3][4][5][6][7][8] = [4] [7][9][10]

Heat from CHPHeat from CHPSupplementary Heat

Jan1.91360017600780084008400920060001800

Feb4.51100015000720084008400660060001200

Mar965001050068008400840021006000800

April12350075006250840075005357***893

May14150055005800812055003929***1871

June16040005200728040002857***2343

July17040004800672040002857***1943

Aug16040004800672040002857***1943

Sep13250065005200728065004643***557

Oct11450085006200840084001006000200

Nov965001050068008400840021006000800

Dec4.11140015400780084008400700060001800

GWhGWhGWhGWhGWhGWhGWh

TOTALS78.4853.7568.3458.9719.5142.1211.63

Imported ElectricityCHP electricity

Jan18006000

Feb12006000

Mar8006000

April8935357

May18713929

June23432857

July19432857

Aug19432857

Sep5574643

Oct2006000

Nov8006000

Dec18006000

Sheet1

00

00

00

00

00

00

00

00

00

00

00

00

Heat from CHP

Supplementary Heat

kW

Sheet2

Imported Electricity

CHP electricity

kW

Sheet3

*Electricity Out Irrecoverable Losses Useful HeatSection 4: CCGT with CHP Large Scale (1)*

*Gas turbine efficiency Electricity generated: 0.25 * 0.95 = 0.2375 0.25 0.750.125Irrecoverable LossesEnergy to Steam Turbine= 0.75 0.125 = 0.6250.625Section 4: CCGT with CHP Large Scale (2)*

TemperatureTemperature (K)Inlet temperature to gas turbine1127 oC1400Exhaust temperature from gas turbine660 oC933Losses from stack, generator and WHB12.50%Note Error in Isentropic efficiency of both turbines75.0%HandoutGenerator efficiencies95.0%

* steam turbine efficiency Mechanical power to generator = 0.425 * 0.625 = 0.2656Heat to Condenser = 0.625 0.2656 = 0.3594Electricity out = 0.95 * 0.2656 = 0.25230.3594Section 4: CCGT with CHP Large Scale (3)*

TemperatureTemperature (K)Inlet temperature to steam turbine577 oC850Condenser temperature95 oC368

*Station use of electricity= (0.2375 + 0.25230) * 0.04 = 0.196Useful Heat = 0.3594*(1 0.152) = 0.3048Section 4: CCGT with CHP Large Scale (4)*

Station use of electricity4.0%Distribution losses on heating mains15.2%

*Summary of SchemeFor each unit of fuelElectricity available = 0.470 unitsHeat sent out = 0.3594 unitsStation efficiency = 0.470 + 0.3594 = 82.9%But heat is lost form mains so only 0.3048 is actually usefulOverall system efficiency = 0.47 + 0.3048 = 77.5% Section 4: CCGT with CHP Large Scale (5)

*Section 5: Heat Recovery Systems and Heat PumpsNBSLM03E (2010)Low Carbon Technologies and SolutionsN.K. Tovey () M.A, PhD, CEng, MICE, CEnv

*Parallel Plate Heat ExchangerCold Fluid InHot Fluid InSection 5: Heat Recovery Systems and Heat Pumps

*Parallel Flow Shell and Tube Exchanger

Cold Fluid InHot Fluid InDistanceHot FluidCold FluidTemperatureSection 5: Heat Recovery Systems and Heat PumpsInefficient: maximum temperature achieved is ~ 50% of temperature difference

*Contra Flow Shell and Tube ExchangerHot Fluid InDistanceTemperatureCold Fluid InSection 5: Heat Recovery Systems and Heat PumpsTemperature of heated fluid slightly less than original effluent hot fluid more efficient

*Operation of Regenerative Heat ExchangersStale air passes through Exchanger A and heats it up before exhausting to atmosphereFresh Air is heated by exchanger B before going into buildingStale air passes through Exchanger B and heats it up before exhausting to atmosphereFresh Air is heated by exchanger A before going into buildingAfter ~ 90 seconds the flaps switch over.Section 5: Regenerative Heat Exchangers*

*A heat pump or refrigerator consists of four parts:-1) an evaporator (operating under low pressure and temperature)3) a condenser (operating under high pressure and temperature)4) a throttle value to reduce the pressure from high to low.2) a compressor to raise the pressure of the working fluidSection 5: Refrigerators andHeat Pumps*

**Any low grade source of heat may be used Typically coils buried in garden Bore holes Water bodies AirExample of roof solar panel with Heat PumpHeat recovery in industrial processesA heat pump delivers 3, 4, or even 5 times as much heat as electricity put in. Section 5: Heat PumpsWorking with thermodynamics not against it!

*Performance is measured by Coefficient of Performance (COP)Theoretical Performance is defined by Carnot Relationship and may be large 6 10 as much heat is delivered as energy (electricity) input. Practical COP in excess of 3.i.e. Three times as much heat is obtained as work put in.Remaining heat comes from the environmentThe closer the temperature difference, the better the COPCan be used for efficient heat recovery Can recover the energy lost in electricity generation Will out perform even a gas condensing boilerWorking with Thermodynamics - NOT against itSection 5: Heat Pumps*

*The Norwich Heat Pump 1944-6Original Paper by John Sumner Proc. Institution of Mechanical Engineers (1947): Vol 156 p 338*

*The building was unique - the very first heat pump in the UK.Installed during in early 1940s during the War.Built from individual components which were not ideal.Compressor was second hand built in early 1920s ! for Ice making.The evaporator and condenser had to be built specifically on site.Refrigerant choice was limited during War - only sulphur dioxide was possible.A COP of 3.45 was obtained - as measured over 2 years.Even in 1940s, the heat pump was shown to perform better than older coal fired boiler. The Norwich Heat Pump 1944-6The History of the Site

*The Norwich Heat Pump - note the shape of the columnsThe History of the SiteThe Norwich Heat Pump 1944-6

*Schematic of the Norwich Heat Pump- from John Sumners Book - Heat PumpsThe History of the SiteThe Norwich Heat Pump 1944-6*

*The Norwich Heat Pump Building as it is today*

*13.6 Types of Heat Pump For Space Heating Purposes: The heat source with water and the ground will involve laying coils of pipes in the relevant medium passing water, with anti-freeze to the heat exchanger. In air-source heat pumps, air can be passed directly through the heat exchanger.For Process Heat Schemes: the source may be a heat exchanger in the effluent of one process

Heat Sourceairwaterground

HeatSinkairair to airwater to airground to airwaterair to waterwater to waterground to watersolidair to solidwater to solidground to solid

*Some Examples13.6 Types of Heat Pump

Air to air:- Refrigeration vehicles, many simple heat pumps, most air-conditioning plants.Air to water:-Proposed UEA scheme in 1981Air to solid? May be relevant in a case where heat recovery from exhaust air is recovered - ?? A variant of ZICER - possible use in Academic Building East??Water to air Ditchingham Primary SchoolWater to waterNorwich Electricity Board Heat Pump during War; Royal Festival Hall. Southampton Geothermal Scheme.Water to solidProposed Duke Street Refurbishmentground to air? A scheme with cooling in summer and heating in winter with inter-seasonal heat storageground to waterENV demonstration scheme. No longer availableground to solidJohn Sumner's Bungalow: Now the preferred route for heat pumps except where water source is available

*

Advantages of Water as a heat sourceReadily Available Air Sources Heat Pumps are generally cheaperDisadvantages of Air as a heat sourceNoise on external fansSource temperature low when most heat needed: hence performance inferior at times of greatest needSource temperature varies greatly:- hence cannot optimise design External Heat Exchanger can freeze and provision must be made for defrosting.Generally heat pumps are not as robust as with other heat sourcesSection 5: Heat Pumps Heat Sources*

*

Advantages of Water as a heat sourcesource temperature normally higher than air or ground in winter: hence improved COP source temperature nearly constant: hence design can be optimised Can be either a water body or pumped from a bore holeDisadvantages of Water as a heat sourcenot readily availablesize of water body must be consistent with total heat demand e.g. a small pond would freeze rapidly and negate many advantages large pond/lake/river avoid this issue.

Section 5: Heat Pumps Heat Sources*

*Advantages of Ground as a heat sourcereasonable availabilitymoderate source temperature - better than air, worse than water limited variation in source temperature: optimisation of design possible ground source heat pumps are more robust than air-source devices. can be used to store heat rejected from cooling in summer to accelerate ground heat recharge and improve CO{P in early part of following winter.Disadvantages of Ground as a heat sourcecapital cost is great if retro-fitted land area can be large - for a carefully engineered system an area 1.5 twice the total floor area of the building is required for systems in UK.Some contractors try to reduce area of heat source resulting in inadequate heat provision in severe weather.

Section 5: Heat Pumps Heat Sources*

*

Advantages of Air as a heat supply mediumrelatively low temperature: hence good COPpossibility of heat recovery using mechanical ventilation. Possibility of use with air-conditioning and inter-seasonal heat store if used with ground source.Disadvantages of Air as a heat supply mediumcan only be fitted into warm air systems which require large ducts and less easy to install restrospectively than small bore hot water systems.. cannot be used with most current Central Heating systems in UK.

Section 5: Heat Pumps Heat Supply*

*

Advantages of Water as a heat supply mediummore compact: can be incorporated with existing systems in use in UK Disadvantages of Water as a heat supply mediumhigh operating temperature: hence lower COPDifficult to incorporate heat recovery

Section 5: Heat Pumps Heat Supply*

*

Advantages of under floor heating as a heat supply mediumLow temperature ~35o C compared to ~ 60o C for hot water systems Possibility of using heat store in fabric. Disadvantages of under floor heating as a heat supply mediumCannot be fitted retrospectively: must be installed at time of construction. Difficult to incorporate ventilation heat recovery

Section 5: Heat Pumps Heat Supply*

*Section 5: The Winnington Tovey Heat Pump*

*Absorption Heat PumpsThe Win - Win opportunity More electricity can be generated in summer Less electricity demand in summer More income from exported electricitySection 5: Absorption Heat Pumps*

*Diesel or Gas driven Heat PumpAdditional Heat can be obtained from exhaust gases*Section 5: Other types of Heat Pump

* Separate consumption into components: base load for lighting appliances etc. Air-conditioning load: Gradient of line = 75 kW oC-1Base LoadCooling LoadA large hotel complexSection 5: Using an Air-Conditioner in a Tropical Climate (1)

*Gradient of line = 75 kW oC-1But coefficient of performance is say 2.5 actual cooling load is 2.5 * 75 = 225 kWoC-1What is energy consumption for cooling over a period?Degree-days are a measure of cooling (or heating) requirements (see section 11.5)Heating and Cooling Degree-Day data are often available.CDD: Base temperature is say 20. external temperature . 30 CDD = 10 for that dayExternal temperature . 40 CDD = 20Cooling degree days is sum of CDD over relevant period.

If CDD over period is 3000 (a typical value for some tropical countries)Total demand of electricity= 75 * 3000 * 24 = 54000000 kWh = 5 400 MWhIf Carbon factor is 800 kg / MWh,Total Carbon emissions associated with cooling = 5400 * 800 = 4320 tonnesSection 5: Using an Air-Conditioner in a Tropical Climate (2)

*Our Wasteful Society650 m21 mWe behave as though we call in the RAFThe Heat Pump is the analogy with the craneSection 5: Applications of Thermodynamics : ConclusionsAcknowledgementJohn Summer for many lengthy discussions on heat pumps and his idea about the crane

***********