Energy quality management and low energy architecture
Transcript of Energy quality management and low energy architecture
Energy quality management and low energy architecture Folke Bjรถrk
Professor
Siir Kilkis Marco Molinari
Ph.D. Tech. Lic.
Building Technology
KTH, the Royal Institute of Technology
Stockholm, Sweden
Building technology
The subject includes development by design, construction and dimensioning, and also by the building process, to improve building constructions and in particular the building envelope to achieve
โขmoisture safety
โขenergy efficiency and
โขa healthy indoor climate
Low energy architecture
Building design aiming at
โข reducing the heating and cooling demand
โขmaking use of passive building techniques
โขexploiting local renewable sources
โขand utilizing any energy resource efficiently
Energy quality management
What do we mean by that?
โข Energy quality can be expressed as exergy, which measures the useful work potential of a given amount or flow of energy on the supply side.
โข Energy quality management is particularly useful to reduce the primary energy use in the built environment.
โข This is achieved by reducing the heating and cooling demand, making use of passive building techniques, exploiting local renewable sources, and utilizing efficiently non-renewable energy.
Background in the field of exergy
Annexes within IEA ECBCS
โขAnnex 37 โ Low exergy systems for heating and cooling of buildings
โขwww.ecbcs.org/annexes/annex37.htm
โขAnnex 49 โ Low exergy systems for high performance buildings and communities
โขwww.annex49.org
The rational energy management model - REMM
โข Presented by Siir Kilkis
โขwww.diva-portal.org search for Siir Kilkis
Exergy on the supply side
Exergy content in the fuel =potential for useful work
Reference temperature
Possible combustion temperature
Energy content in the fuel
๐sup ๐ = 1 โ๐๐
๐๐ยท ๐๐
Exergy on the demand side
Exergy demand =potential for useful work at the temperature level at the demand side
Reference temperature
Temperature wanted
Energy demand
๐dem ๐ = 1 โ๐๐
๐๐ยท ๐๐
The exergy efficiency ratio ฮจRi
This ratio should be close to 1 for a high efficiency:
The lost work potential from the energy supply will be:
๐๐ ๐ =๐๐๐๐(๐)
๐๐ ๐ข๐(๐)
๐๐ ๐ข๐ โ 1 โ๐๐๐๐๐๐ ๐ข๐
= ๐๐ ๐ข๐ โ 1 โ ๐๐ ๐
Consider efficiency ๐๐
The efficiency in the process is ฮทi, and so for each unit of energy needed an amount P/ ฮทi
is to be spent.
The lost work potential when also considering efficiency:
๐๐ ๐ข๐ โ 1 โ๐๐๐๐๐๐ ๐ข๐
โ1
๐๐= ๐๐ ๐ข๐ โ 1 โ ๐๐ ๐ โ
1
๐๐
Consider CO2
Each unit of energy from the fuel produces an amount ci of CO2, so for meeting the demand of one unit of energy in process i this amount of CO2 is produced:
๐ถ๐2๐ =๐๐๐๐ยท ๐๐
Replace wasted exergy in process i
Somewhere the work potential that was wasted in the process i would really have been needed.
This wasted exergy will be replaced in the process j:
1 โ๐๐
๐๐โ๐๐๐๐โฅ ๐ฟ๐๐ ๐ก ๐ข๐ ๐๐๐ข๐ ๐ค๐๐๐ ๐๐๐ก๐๐๐ก๐๐๐
Work in system j replacing the wasted
work
For a fossil fuel:
So weยดll get the simplification:
Wasted work potential in system i
Work in system j
Replacing the wasted work
๐๐
๐๐โช 1
๐๐๐๐โฅ๐๐๐๐โ 1 โ ๐๐ ๐
Total avoidable CO2-emission
โข In the process j each unit of energy from the fuel produces an amount cj of CO2, so for meeting the demand of one unit of energy in process j this
amount of CO2 is produced:
This is avoidable emission of CO2 for 1 kWh in process j.
โ๐ถ๐2๐ =๐๐๐๐โฅ๐๐๐๐โ 1 โ ๐๐ ๐
We combine direct and avoidable CO2-emissions and get the total emissions:
ฮทT = the efficiency of transmission from power plant to where the energy is to be used
๐ถ๐2๐ = ๐ถ๐2๐ + โ๐ถ๐2๐ =๐๐๐๐+๐๐๐๐ โ ๐๐
โ 1 โ ๐๐ ๐
A case
In a case, we say that the indoor temperature Ta is 295K, which is a typical comfort indoor temperature in the Stockholm area. Tg is 280 K and the Tf for combustion is 2000 K.
Ta= 295 K = 22ยฐC = 71,6ยฐF Tg= 280 K = 7ยฐC = 44,6 ยฐF Tf=2000 K = 1723ยฐC =3133ยฐF
๐๐ ๐ =๐๐๐๐ ๐๐๐ ๐ข๐(๐)
=1 โ๐๐๐๐
1 โ๐๐๐๐
= 1 โ280295
1 โ2802000
= 0,051
0,86= 0,059
The exergy efficiency ratio ฮจRi becomes 0.059
This is not very efficient โ improvements are possible!
Compound CO2-emissions
The value of 0,059 for ฯRi has impacts in the energy system, with primary energy spending and CO2 emissions Per unit ci, cj, ฮทi, ฮทT and Pi, the value of ฮฃCO2i is found to be:
Produce and use
fossil energy
as efficient
as possible
Use sustainable sources of energy instead of finite
fossil fuels
Reduce demand for energy by avoiding waste and implementing energy-saving measures
The Trias Energica: TU Delft, The Netherlands Senternovem
1
2
3
The Trias Energetica concept
Plan for renewable energy
Avoid fossil
fuel
Use any energy as efficient as
ever possible
Consider the exergy concept
Reduce demand for energy
1
2
3
A modified trias โ considering exergy
Conclusions
โข Exergy is a vital aspect for low energy architecture and low CO2 emissions
โข The Rational energy management model (REMM) further show how integration of the building in the broader perspective of the community level is crucial to curb building-related CO2 emissions.
โข Energy quality management is a way to proceed towards a sustainable development.
Thank you!
Folke Bjรถrk
Professor
Siir Kilkis Marco Molinari
Ph.D. Tech. Lic.
Building Technology
KTH, the Royal Institute of Technology
Stockholm, Sweden
Background in the field of exergy
Annexes within IEA ECBCS
โขAnnex 37 โ Low exergy systems for heating and cooling of buildings
โขwww.ecbcs.org/annexes/annex37.htm
โขAnnex 49 โ Low exergy systems for high performance buildings and communities
โขwww.annex49.org
The rational energy management model - REMM
โข Presented by Siir Kilkis
โขwww.diva-portal.org search for Siir Kilkis