BUILDING ENERGY SYSTEMS Week 6 7LYM30 Building performance and energy systems simulation
Building District Regional 2
Other challenges» Real challenge: existing buildings» Building + system building = system 3 [Centre for Interactive Research on Sustainability http://cirs.ubc.ca/building]
Energy Academy Europe Orientation Climate ceiling Geothermal energy Daylight BIPV Solar chimney Compact shape Atrium Natural ventilation Underfloor heating Night cooling Heat pump Aquifer thermal storage 5
The trias energetica concept Ability to impact design and building performance Cost of design changes Traditional design process Front-loaded design process 6 [Sefaira]
NZEB and system boundaries 7 REHVA NZEB definition
Example demand side» Consider an office building located in Paris with following annual energy needs (all values are specific values in kwh/(m² a)): 3.8 kwh/(m² a) energy need for heating (space heating, supply air heating and DHW) 11.9 kwh/(m² a) energy need for cooling 21.5 kwh/(m² a) electricity for appliances 10.0 kwh/(m² a) electricity for lighting» Gas boiler for heating with seasonal efficiency of 90%.» For the cooling, free cooling from boreholes (about 1/3 of the need) is used and the rest is covered with mechanical cooling. For borehole cooling, seasonal energy efficiency ratio of 10 is used and for mechanical cooling 3.5.» Ventilation system with specific fan power of 1.2 kw/(m³/s) and the circulation pump of the heating system will use 5.6 kwh/(m² a) electricity.» There is installed a solar PV system providing 15.0 kwh/(m² a), from which 6.0 is utilized in the building and 9.0 is exported to the grid. 8
Example systems side» Gas boiler for heating with seasonal efficiency of 90%.» For the cooling, free cooling from boreholes (about 1/3 of the need) is used and the rest is covered with mechanical cooling. For borehole cooling, seasonal energy efficiency ratio of 10 is used and for mechanical cooling 3.5.» Ventilation system with specific fan power of 1.2 kw/(m³/s) and the circulation pump of the heating system will use 5.6 kwh/(m² a) electricity.» PV system providing 15.0 kwh/(m² a), from which 6.0 is utilized in the building and 9.0 is exported to the grid. 9
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11 REHVA NZEB definition
How to reduce HVAC energy use? Use energy-efficient systems.» Displacement Ventilation» High-temperature cooling systems (e.g., cooling/chilled beam)» Low-temperature heating systems (e.g., floor heating)» Phase change materials (PCM)» Mixed mode ventilation systems» Double skin facade» Advanced control systems (e.g. preheating/cooling, demand driven)» etc. 12
Displacement Ventilation» No need to condition the entire volume» Higher supply air temperature = More free cooling Data based on San Francisco weather files 13 Source : Rob Pena and Kevin Den, Training Course, Estonia 16th June 2009
Impact on delivered energy No need to condition the whole volume Using higher supply are air temperature Source: Modular heat pumps: energy performance http://www.rehva.eu/publications-andresources/hvac-journal/2014/062014/modularheat-pumps-energy-performance/ 14
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16 REHVA NZEB definition
17 [Autodesk]
Primary energy factor 18 [EIA]
Different meanings of zero 19 [Browning Day Mullins Dierdorf Architects]
Different meanings of zero 20 [Browning Day Mullins Dierdorf Architects]
Different meanings of zero 21 [Browning Day Mullins Dierdorf Architects]
22 REHVA NZEB definition
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Need for simulation? 24
BIPV/T - Need for simulation 25 [www.seac.cc]
Net-metering - Need for simulation 26
Energy matching self consumption 27
Energy systems models can quickly become very complex Energy supply system with solar thermal system, GSHP, and EAHP. 28 Source: Natasa Nord, Live Holmedal Qvistgaard, Guangyu Cao, Identifying key design parameters of the integrated energy system for a residential Zero Emission Building in Norway, Renewable Energy
System simulation» Definition: "... predicting the operating quantities within a system (pressures, temperatures, energy and fluid flow rates) at the condition where all energy and material balances, all equations of state of working substances, and all performance characteristics of individual components are satisfied. (ASHRAE 1975)» Consider building dynamics vs. system dynamics 29
Approaches for modeling energy systems A. Ideal system B. System based (e.g. VAV) C. Component based D. Component based in multidomain E. Equation based Conceptual Explicit 30
C - Component based» System built up in terms of individual plant components (e.g. fan, duct, heating coil). 1. input-output based + mixture of modelling methods + piecemeal component development 11-Oct-16 - sequential approach (e.g. control) > solution technique - not integral system - user knowledge - plant definition parameter 31
C - Component based» System built up in terms of individual plant components (e.g. fan, duct, heating coil). 2. conservation equation based (energy, mass flow) + limitations sequential approach 11-Oct-16 - not integral system - user knowledge - plant definition parameters 32
Examples 33
Case: room thermostat Plant - 6 components - 51 parameters 34
The trias energetica concept 35
Energy demand vs. generation Onsite energy generation, kwh/m 2 a RES 1 RES 2 RES 3 RES 4 RES n Design 1 Design 2 Design 3 Design 4 Design n Energy demand, kwh/m 2 a 36 PhD Research Rajesh Kotireddy
Selected renovation options Low insulation Medium insulation Very high insulation Rc wall = 3m 2 K/W Rc roof = 4m 2 K/W U window = 1.43W/m 2 K SHGC = 0.75 Infiltration = 0.60ach PV system = 30m 2 Solar DHW system = 0m 2 Additional investment cost = 23 k Rc wall = 5m 2 K/W Rc roof = 6m 2 K/W U window = 1.01W/m 2 K SHGC = 0.4 Infiltration = 0.36ach PV system = 25m 2 Solar DHW system = 2.5m 2 Additional investment cost = 29 k Rc wall = 10m 2 K/W Rc roof = 10m 2 K U window = 0.4W/m 2 K SHGC = 0.4 Infiltration = 0.12ach PV system = 15m 2 Solar DHW system = 5m 2 Additional investment cost = 38 k 37 PhD Research Rajesh Kotireddy
Scenarios Scenarios 1-4 Working, retired 18-22 C 14-18 C 0.9-1.5 ach 1-3 W/m 2 60-180 L/p/day 1-3 W/m 2 ON/OFF Radiation (200-350 W/m 2 ) Tindoor > 24 C NEN 5060-2008 G, W, G+, W+ 38 PhD Research Rajesh Kotireddy
Global cost Cost of investment, replacement and operational Calculated for period of 30 years service life span of energy systems Global cost, /30 years Performance variation across all scenarios x 10 4 9 8 7 6 5 4 3 1 2 3 4 Robustness -Global cost, /30 years Performance robustness across all scenarios x 10 4 4 3 2 1 0 1 2 3 4 0 k 23 k 29 k 38 k 0 k 23 k 29 k 38 k 39 PhD Research Rajesh Kotireddy
Thermal comfort Hours above adaptive temperature limits proposed by Peeters et al., 2009 Calculated for occupancy hours in a year Performance variation across all scenarios Performance robustness across all scenarios Overheating hours, h/a 300 250 200 150 100 50 0 Robustness - overheating hours, h/a 200 150 100 50 0 1 2 3 4 1 2 3 4 0 k 23 k 29 k 38 k 0 k 23 k 29 k 38 k 40 PhD Research Rajesh Kotireddy
CO2 emissions EF = CO 2 emission factor Embodied emissions are not taken into account Performance variation across all scenarios Performance robustness across all scenarios CO 2 emissions, kgco 2 /a 10000 8000 6000 4000 2000 0 Robustness -CO 2 emissions, kgco 2 /a 10000 8000 6000 4000 2000 0 1 2 3 4 1 2 3 4 0 k 23 k 29 k 38 k 0 k 23 k 29 k 38 k 41 PhD Research Rajesh Kotireddy
Summary - Design considerations» Form of Energy electricity? thermal energy? (at what temperature?)» Generation Characteristics environment dependent solar radiation, wind availability, soil properties» Design Objectives / Evaluation Criteria Energy generation Life-cycle cost-effectiveness (unit cost, life-span, energy price...) Life-cycle carbon footprint (embodied carbon, life-span, comparative advantages...) Environmental Impact» Design Limitation / Trade-off financial resource limit the amount of capital investment land availability limit the project size 42
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Helioscope 44
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