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Table 1 Nomenclature energy concept

From: Upscaling a district heating system based on biogas cogeneration and heat pumps

Term Signification
η chp,e , η chp,t CHP electric and thermal efficiency
η b,t Boiler thermal efficiency
η sto,ht High temperature (HT) thermal storage average efficiency
η sto,lt Low temperature (LT) thermal storage average efficiency
η distr DH distribution network average efficiency
COPhp Heat pump (HP) coefficient of performance (COP)
COP c Refrigeration chiller COP
f netw,p Fraction of required electric pump energy for network pumps related to transmitted thermal energy of the network
ϕ biogas, ϕ ngas Biogas supply to CHP, natural gas supply to boilers (m 3/h)
LHV Lower heating value (MJ/m 3)
\(\dot {Q}_{\text {biogas}}\) or \(\dot {Q}_{\text {ngas}}\) Fuel-related thermal energy input (kW)
Q dh,demand,h Total DH heating demand of (n) connected houses (GJ)
Q hp,demand,h Total heating energy demand of (m) houses with a heat pump (GJ)
Q hp,source Total low temperature source heat for the heat pumps (GJ)
Q dhw, Q sh Domestic hot water demand and space heating demand (GJ)
Q demand,c , Q dh,c , Q hp,c Cooling energy demand, for DH network houses, for houses with heat pumps (GJ)
\(\dot {E}_{\text {chp}}\) CHP electric rated power (kW)
\(\dot {Q}_{\text {chp}}\) CHP thermal rated power (kW)
\(\dot {Q}_{b}\) Boiler thermal rated power (kW)
t op,chp and t op,b Full load operational hours of the CHP and boiler (h/year)
\(\dot {E}_{c}\), \(\dot {Q}_{c}\) Refrigeration chiller electric rated power and cooling rate (kW)