Rainfed scenario

Table 3.11: Energy supply scenarios. Rainfed Fruit hulls and seed

shells Energy generation scheme Used as fertilizer a11 Conventional oil boiler a12 Conventional coal boiler a21 Conventional NG boiler

f11 Diesel genset with heat utilization block f12 NG genset with heat utilization block g NG CHP Microturbine

Used as fuel h11 Anaerobic digester + CHP externally fired micro gas turbine h12 Integrated biomass gasifier + CHP gas engine genset

3.6.1 Basic configuration: conventional oil-, coal- or natural gas-fired boiler and imported electricity.

Models a11, a12 and a21 (Table 3.12) were considered as the basically simplest and required minimum investment configurations. Heat, required for the process in the form of steam, is generated by an on-site boiler. Electricity is purchased from the Indian National Grid.

Table 3.12: Basic configuration Models:

Oil boiler a11

Coal boiler a12

NG boiler a21

3.6.2 Optimized fossil fuelled plant: combined heat and power (CHP)

Table 3.13: Optimized fossil fuelled plant Models:

Diesel genset with heat utilization block (HUB) f11

NG genset with heat utilization block (HUB) f12

NG CHP Microturbine g

Gas, diesel and dual-fuel (DF) powered reciprocating engines are all used in cogeneration plants (Table 3.13). However, gas engines are generally preferred due to considerably lower exhaust emissions, good performance with CHP applications, and high efficiency of fuel utilization. Gas engines also produce nearly none particulates, so in CHP applications, exhaust heat boilers and HRSGs are not sooted up. Sooting can compromise plant termal efficiency and be a significant maintenance problem when diesel (heavy fuel oil) engines are utilized (Hunt: 2009).

Medium-speed diesel and gas reciprocating engines can achieve electrical efficiency of up to 47% for engines larger than 3 MWe. However, the utilization factor for a CHP plant might be only 50-60% as exhaust heat might not always be required. Also, generators driven by large reciprocating engines can reach a net fuel efficiency for electricity generations equal or more than 44% simple cycle, and 80-90% for CHP, depending on temperature of the heat used (approximately 38% of fuel energy should preferably used for district heating or industrial processes) (Ibid.).

Cummins Spark-Ignited Generator Set, Model GGHH equipped with Ford Heavy-Duty - Rugged 4-cycle industrial spark-ignited engine WSG-1068 has been used as a Natural Gas genset for energy (electricity and heat) supply estimations for the small-scale (plant capacity: 10.0 t of Jatropha oilseed per day, ~1,000.0 t of biodiesel per annum) biodiesel plant in Rainfed I and Rainfed II scenarios in Model f12. Technical characteristics for Cummins GGHH genset presented at the Table 3.14.

Table 3.14: Technical characteristics for Cummins Spark-Ignited Generator Set.

Model GGHH. Base engine: Ford WSG-1068, Turbocharged¹⁾

Power MWe 0.105

Net thermal output MWth 0.163

Operating hours khr/a 8

Power production GWhe/a 0.84

TJe/a 3.0

a) Standard Fuel: Natural Gas or Propane¹⁾;

b) Efficiency: US DOE Advanced Reciprocating Engine Systems (ARES) programme Original equipment manufacturers (OEMs) Waukesha, Caterpillar and Cummins: thermal ~45-47%, 2010 target is 50%²⁾;

c) In case of biogas usage in a gas engine, installed at the biogas plant with 500 kWe - electrical efficiency of 37.5%, thermal efficiency of 42.5%, and methane loses of 0.5%³⁾

Sources:

1) www.cummins.com;

2) COSPP: January-February 2007;

3) COSPP: July-August 2009

Volvo Penta Genset equipped with TD720GE engine has been used as a Diesel genset for energy (electricity and heat) supply estimations for the small-scale (plant capacity: 10.0 t of Jatropha oilseed per day, ~1,000.0 t of biodiesel per annum) biodiesel plant in Rainfed I and Rainfed II scenarios in Model f11. Technical characteristics for Volvo Penta Genset presented at the Table 3.15.

Table 3.15: Technical characteristics for Volvo Penta Genset.

Base engine: TD720GE

Power MWe 0.117

Operating hours khr/a 8

Power production GWhe/a 0.94

TJe/a 3.4

Hot water after HUB TJ/a 4.09

Diesel consumption TJ/a 8.46

Genset elec. efficiency 40%

Genset total efficiency 84%

Elec/heat ratio 0.82

Note: Fuel: diesel with caloric value 42.7 GJ/t and a density of 0.84 kg/liter Source: www.volvopenta.com

A Heat Transfer System (HTS) allows utilization of the waste heat of the gas and diesel engines through heating the intermediate liquid heat carrier up to 95-98°C. In the cogeneration plants this intermediate carrier is used for production of hot water in the end heat exchanger (EndHEX) of district heating system (DHS), whereas in the trigeneration plants it is used as heating medium in the generator of absorption refrigerating machine (ARM).

The HTS described above is the main part of the Heat Utilization Blocks (HUB), which also contains system of control, instrumentation, protection and indication, and can be installed using the special supporting structures inside of cogeneration and trigeneration plants or inside of the transportable containers.

A typical scheme of the HTS for a reciprocating diesel or gas engine of small-to-medium size is presented in Figure 3.4. Usually such a diesel (DE) or gas engine (GE) is delivered together with the electric generator (EG) and equipped with the cooling system, consisting of: combustion air cooler (CAC) - for engines with enhanced turbocharging pressure, exhaust manifold cooler (EMC), lube oil cooler (LOC), jacket water cooler (JWC), as well as of liquid cooling medium pump (LMP), providing circulation of cooling medium between the mentioned coolers and air fan radiator (AFR). In the regime of diesel engine or gas engine operation without heat recovery or with a partial use of this heat, radiator provides dissipation of waste heat from the full or a partial stream of cooling medium respectively into surrounding. At the same time the exhaust gas is removed to atmosphere through a silencer.

Figure 3.4: The Heat Transfer System (HTS) for a reciprocating diesel or gas engine

Source: MEEC: 2007. Available at: http://meec.kangu.ru/service/epc_services_3.html

The HTS consists of of water-to-water heat exchanger (WWHEX) installed parallel to the AFR and equipped with temperature controller (TC), gas-to-water heat exchanger (GWHEX) installed in the HTS downstream of the WWHEX, exhaust gas bypass damper (GBD) providing release of exhaust gas from the diesel engine or gas engine through the GWHEX to stack or to silencer, and electric motor-driven heat carrier pump (HCP) providing circulation of the intermediate heat carrier through the mentioned heat exchangers of the Heat Transfer System (HTS) to and from the end heat exchanger (EndHEX). In the most cases the existing heat transfer equipment of the boiler house as the EndHEX is utilised.

Optionally, the special heat exchanger (HEX) for district heating system or supply a generator of the ARM with intermediate heat carrier as its heating medium could be manufactures and installed as well (Sinatov: pers. comm.).

3.6.3 Combined Heat and Power (CHP) plant fuelled by biomass

Table 3.16: CHP fuelled by biomass Models:

Anaerobic digester + CHP externally fired micro gas turbine h11 Integrated biomass gasifier + CHP gas engine genset h12

The externally fired micro gas turbine (EFmGT) process and plant layout presented at Figures 3.5 and 3.6. EFmGT (or in another terms IFGT - Indirectly-fired microturbine) is based on a gas turbine cycle, where the traditional direct combustion is replaced with a heat exchanger that heats up the working media, usually air (Savola, et. al.: no date, Bram, et.

al.: 2004, Ferreira & Pilidis: 2001, Kautz & Hansen: no date).

Figure 3.5: The externally fired micro gas turbine (EFmGT) plant layout^a)

Note: The IFGT demonstration plant at the Vrija Univeriteit in Brussels Sources:

1) Bram, et. al.: 2004;

2) Savola, et. al.: no date

Figure 3.6: The externally fired gas turbine process

Source: Kautz & Hansen: no date

ABB/Volvo Turbec T100 micro gas turbine design data and technical characteristics (Tables 3.17 & 3.18) has been used for energy (electricity and heat) supply estimations for the small-scale biodiesel plant in Rainfed I and Rainfed II scenarios in Models g and h11.

Table 3.17: Design data for Turbec T100 micro gas turbine (ABB/Volvo)

Net electric output 100 kW

Thermal power input 333 kJ/s

Turbine power 281.89 kW

Compressor power 158.97 kW

Net electric efficiency, ISO 30.0

Fuel type Natural gas

Exhaust gas temperature 650 °C

Air temperature compressor outlet 214 °C

Gas temperature turbine inlet 950 °C

Gas temperature after recuperator 270 °C

Mass flow air 0.7833 kg/s

Heat exchanger area in the recuperator 164 m²

Note: The T100 unit includes a heat recovery system for hot water production Source: Kautz & Hansen (no date).

Table 3.18: Technical characteristics for Microturbine Turbec T100 CHP system

Power MWe 0.105

Net thermal output MWth 0.163

Operating hours khr/a 8

Power production GWhe/a 0.84

TJe/a 3.0

Elec/heat ratio 0.64 0.64 - www.turbec.com;

0.62 - Energy Nexus Group. 2002 Notes:

a) The T100 unit includes a heat recovery system for hot water production:

1) 163 F (77.7^oC) - Energy Nexus Group;

180-220 F (82.2-104.4^oC) - www.energysolutionscenter.org;

2) 167 kW (570,000 Btu/hr) - www.turbec.com;

163 kW (0.555 MMBtu/hr) - Energy Nexus Group. 2002 Sources:

1) Kautz & Hansen (no date). The Externally Fired Gas Turbine (EFGT Cycle) and Simulation of Key Components;

2) www.turbec.com;

3) EcoPoly Best Practice Sheet "OMES". DONG Energy. Gentofte: Denmark. OMES. 2007;

4) Energy Solutions Center Inc. (no date). Microturbine CHP Systems. Washington, D.C.

5) Energy Nexus Group. (March 2002). Technology Characterization: Microturbines, Virginia: USA;

6) Ferreira & Pilidis: 2001

Quite staggering is the emergence of renewable CHP facilities. Novel models of used in CHP applications reciprocating engines can burn biofuels. Thus, in recently designed Belgian Greenpower-owned CHP project a 9.0 MW Wärtsilä 20V32 engine, equipped also with selective catalytic reduction (SCR), will be the first to burn crude Jatropha oil (Hunt: 2009).

Recently established in California the Self-Generation Incentive Program (SGIP), administred by the California Public Utilities Program (CPUP), already represents about 60 facilities, approximately 30 MW of the CHP capacity, powered by renewable fuel sources, such as biogas (COSPP: March-April 2009). Besides, a UK-based enterprise Dalkia, announced a new eco2synergy service, which offers to customers an installation of CHP units range from 30 kW to 3 MW capable to operate using biogas, biomass, bio-diesel, landfill gas and conventional fuels (Ibid.).