Thermal energy need in Helsinki Metropolitan Area

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Scope

Defines how thermal energy need will change in the future in Helsinki metropolitan area. Calculations are done by day degree method which is explained here .

Definition

Data

Consumption of district heating in Helsinki metropolitan area in year 2007 .

Building stock of Helsinki metropolitan area .

Helsinki Metropolitan area Council's (YTV) report of floor area and population changes in Helsinki metropolitan area to 2025

Global warming and changes in outdoor temperature.

Unit

GWh

Formula

Q_h = U * A(T_in-T_out) * t where Q_h = Heat flow from building to surroundings, U = Buildings overall heat transfer coefficient, A = Area about which the heat will go trough, T_in = Indoor temperature, T_out = Outdoor temperature and t = Time period of the transfer. Thermal energy what is needed for warm tap water can be calculated as Q_w = c_p,w * p_w * q_m,w * (T_w,warm - T_w,cold) * t where Q_w = Thermal energy needed for warm tap water, p_w = Water density, c_p,w = Specific heat capacity for water, T_w,warm = Temperature of warm tap water and T_w,cold = Temperature of cold tap water. Other thermal energy leaks are estimated to be negligible. A city’s need of thermal energy in a year can be then estimated to be sum of single buildings need of thermal energy. Thus a city’s total need of thermal energy can be calculated as Q_total = Q_w + Q_h where Q_total = Year need of thermal energy in city, Q_h = Heat flow from building to surroundings and Q_w = Thermal energy needed for warm tap water.