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Contents
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; Heating consumption of buildings.
Definition
Data
In 2007 9751 GWh thermal energy was consumed in district heating buildings in Helsinki Metropolitan area [1]. By using day degree method and statistics of population in the area and water consumption per inhabitant, we can calculate that of thermal energy 350 GWh was used to heat tap water.
Thus overall heat transfer coefficient U was in district heating buildings 16,08 kWh/m2 in Helsinki, 14,04 kWh/m2 in Vantaa, 15,44 kWh/m2 in Espoo and 28,58 kWh/m2 in Kauniainen. If we estimate that in district heating and other buildings have same overall heat transfer coefficient, then we can calculate that total thermal energy consumption in Helsinki Metropolitan area was 12 413 GWh in 2007.
NOTE!!! District heating buildings are mainly apartment buildings and other buildings mainly separate residential houses. The U-value is higher in separate residential buildings, but because at the moment there are no way to determine other buildings U-value, this estimation is made!
For future scenarios we need to estimate how the outdoor temperature and buildings energy efficiencies will evolve. If we use Helsinki Metropolitan area Council (YTV) report of future changes and floor area and population estimations in it, we can calculate that in 2025 thermal energy need is 15 150 GWh.
Total heat demand in cities, if only floor area increase is taken into account | |||||
. | 2007 | 2013 | 2020 | 2025 | 2030 |
. | [GWh] | [GWh] | [GWh] | [GWh] | [GWh] |
Helsinki | 7 457,69 | 7859,143563 | 8327,503495 | 8662,046304 | 8996,589113 |
Vantaa | 2 118,15 | 2312,119471 | 2538,421663 | 2700,066086 | 2861,710509 |
Espoo | 2 661,25 | 2963,875142 | 3316,943568 | 3569,1353 | 3821,327033 |
Kauniainen | 176,13 | 190,1070909 | 206,412201 | 218,0587083 | 229,7052155 |
Total | 12 413,21 | 13 325,25 | 14 389,28 | 15 149,31 | 15 909,33 |
Taking global warming and building stocks improving energy efficiency into account thermal energy need estimation for future years can be made more accurate. By YTV's estimations in 2025 473 GWh thermal energy is needed for warm tap water and 14 650 GWh for heating buildings. Finnish meterology institute estimates that outdoor temperature will increase about 1 oC to year 2030 from year 2007. If then estimated that outdoor temperature is 0,7826 oC higher than it was in 2007, then the energy needed for heating buildings is 13 540 GWh.
NOTE! CLAIH-results will be more accurate for outdoor temperature estimations?
Buildings energy efficiencies are improving all the time and in 2010 law will require 40 % better overall heat transfer coefficients from buildings. If then estimated that all new buildings and renewed buildings will have 40 % better overall heat transfer coefficient than buildings in 2007, then thermal energy needed in Helsinki Metropolitan area in 2025 is 13 110 GWh. This would mean that in a year total thermal energy need increases 38,7 GWh in Helsinki Metropolitan area.
Causality
Unit
GWh
Formula
All the calculations made in excel table, which can be found here File:Assessment of small-scale energy production in Helsinki Metropolitan area.zip. Need of thermal energy calculations are found in worksheet named "need of thermal energy".
Formulas used in calculations:
Qh = U * A * (Tin-Tout) * t where Qh = Heat flow from building to surroundings, U = Buildings overall heat transfer coefficient, A = Buildings total surface area (floor, walls and roof), Tin = Indoor temperature, Tout = Outdoor temperature and t = Time period of the transfer.
Thermal energy what is needed for warm tap water can be calculated as
Qw = cp,w * pw * qm,w * (Tw,warm - Tw,cold) * t where Qw = Thermal energy needed for warm tap water, pw = Water density, cp,w = Specific heat capacity for water, Tw,warm = Temperature of warm tap water and Tw,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
Qtotal = Qw + Qh where Qtotal = Year need of thermal energy in city, Qh = Heat flow from building to surroundings and Qw = Thermal energy needed for warm tap water.
Result
Total need of thermal energy | 2007 | 2013 | 2020 | 2025 | 2030 |
. | [GWh] | [GWh] | [GWh] | [GWh] | [GWh] |
Helsinki | 7 457,69 | 7477,097544 | 7499,737122 | 7515,908248 | 7532,079375 |
Vantaa | 2 118,15 | 2194,713213 | 2284,041438 | 2347,847312 | 2411,653187 |
Espoo | 2 661,25 | 2806,956036 | 2976,95217 | 3098,377981 | 3219,803792 |
Kauniainen | 176,13 | 180,4435801 | 185,4745944 | 189,068176 | 192,6617576 |
TOTAL | 12 413,21 | 12 659,21 | 12 946,21 | 13 110,50 | 13 356,20 |
See also
References
- ↑ Adato Energia Oy. 2008. District heating in Finland 2007. Kaukolämpötilastot 2007 (in Finnish)
- ↑ Helsingin Vesi. 2009. Water consumption in Helsinki area (in Finnish).
- ↑ Adato Energia Oy. 2008. District heating in Finland. Kaukolämpötilasto 2007
- ↑ Statistics of Finland. 2008. Building stock 2000 & 2007
- ↑ Helsinki metropolitan area Council. 2003. PKS tulevaisuudenkuva 2025 (in Finnish)