ASHRAE Journal - September 2009 - 34

electricity, it can be shown that the overall system efficiency is approximately 34% (solar energy to equivalent electricity). This assumes that the equivalent electrical energy required by a vapor compression chiller operates at a COP of 3. For now, the balance of thermal power, electrical power and chilled water produced with such a system compared to the average office building energy demand splits (electricity and cooling) was not evaluated. The installation and collection surface of this system will likely be lower than that achievable by roof mounted photovoltaic to account for the tracking system, maintenance requirements and thermal system components. A roof coverage factor of 66% was assumed. Table 3 summarizes the solar collector conversion efficiencies used for the assumed rooftop-mounted renewable energy systems that needs to match the building energy demand. Towards Zero Energy Building Figure 5: Parabolic trough solar collection system with steam turbine generator, absorption chiller and domestic hot-water heating. Renewable Technology Photovoltaic Cell Solar Thermal Parabolic Trough Solar Conversion Efficiency 15% 34% Roof Coverage Factor 0.75 0.66 Table 3: Assumed renewable energy conversion efficiency. Building Energy Simulation Scenario (Option) Renewable Energy Used Non-Tracking Photovoltaic 1 1.98 2 2.05 3 2.06 4 2.02 5 2.08 6 2.08 7 2.53 8 3.14 The aim of the article is to illustrate Tracking Photovoltaic 2.46 2.55 2.56 2.51 2.58 2.59 3.15 3.90 the available building floor space that Concentrating Parabolic Trough theoretically can be supported by a 3.45 3.57 3.58 3.52 3.62 3.63 4.41 5.46 Solar Collector (PTSC) roof-mounted renewable energy (solar) technology. One way to simplify this is Table 4: Effective number of floors to match roof-mounted renewable energy production (solar). to describe the balance between available Non-Tracking Photovoltaic solar power and required building energy Tracking Photovoltaic as the number of floors of the modeled Concentrating PTSC 6 building that can be stacked while still achieving net zero energy. This ultimately 4 reduces the calculation to the ratio of an2 nual available solar energy (kWh/m2) per 0 technology discussed and the modeled Option 1 Option 2 building scenario total energy demand Option 3 (kWh/m2). This ratio is number of floors Option 4 Option 5 allowed to achieve net zero energy on a Option 6 site that can use all of its roof and buildOption 7 Option 8 ing footprint to install a solar collection device that produces electricity or its Figure 6: Effective number of floors to match roof mounted renewable energy production (solar). equivalent. Table 4 and Figure 6 show the number of stories for the ber of floors that can be supported, for the simulated cases Opdifferent building arrangements coupled with the three solar tions 1 through 6, is two for typical photovoltaic production. The technologies discussed here. The results show that the maximum influence of the building façade has a significant influence on height for a building with a standard efficiency (Scenarios 1 the solar gains transmitted into the building. However, selecting through 6) is approximately between two and three stories. proper window-to-wall ratios, proper and ample shading for imFor the case with reduced internal gains (plug and lighting), portant well-exposed façades is not sufficient to create buildings the building height can go to four or five stories based on the that can support more than three stories with renewable energy. assumptions used. Significant energy demands are attributed to the building The calculations suggest that even in an area with high solar lighting load, as well as the treatment of humid fresh air. If exposure and good solar energy production the maximum num- significant savings (25% or 50%) can be achieved in lowering 34 ASHRAE Journal ashrae.org September 2009

ASHRAE Journal - September 2009

Table of Contents for the Digital Edition of ASHRAE Journal - September 2009

ASHRAE Journal - September 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
Getting to Net Zero
Feature Articles
How High Can You Go? Building Height and Net Zero
Lab for Learning
Solar Hot-Water Heating System: Lessons Learned
50th Anniversary—Low Pressure Steam Heating Systems
Building Sciences
Products
Emerging Technologies
People
Classified Advertising
Advertisers Index
ASHRAE Journal - September 2009 - ASHRAE Journal - September 2009
ASHRAE Journal - September 2009 - Cover2
ASHRAE Journal - September 2009 - 1
ASHRAE Journal - September 2009 - 2
ASHRAE Journal - September 2009 - Contents
ASHRAE Journal - September 2009 - 4
ASHRAE Journal - September 2009 - Commentary
ASHRAE Journal - September 2009 - Industry News
ASHRAE Journal - September 2009 - 7
ASHRAE Journal - September 2009 - 8
ASHRAE Journal - September 2009 - 9
ASHRAE Journal - September 2009 - Letters
ASHRAE Journal - September 2009 - 11
ASHRAE Journal - September 2009 - 12
ASHRAE Journal - September 2009 - 13
ASHRAE Journal - September 2009 - 14
ASHRAE Journal - September 2009 - 15
ASHRAE Journal - September 2009 - Meetings and Shows
ASHRAE Journal - September 2009 - 17
ASHRAE Journal - September 2009 - Feature Articles
ASHRAE Journal - September 2009 - 19
ASHRAE Journal - September 2009 - 20
ASHRAE Journal - September 2009 - 21
ASHRAE Journal - September 2009 - 22
ASHRAE Journal - September 2009 - 23
ASHRAE Journal - September 2009 - 24
ASHRAE Journal - September 2009 - 25
ASHRAE Journal - September 2009 - How High Can You Go? Building Height and Net Zero
ASHRAE Journal - September 2009 - 27
ASHRAE Journal - September 2009 - 28
ASHRAE Journal - September 2009 - 29
ASHRAE Journal - September 2009 - 30
ASHRAE Journal - September 2009 - 31
ASHRAE Journal - September 2009 - 32
ASHRAE Journal - September 2009 - 32a
ASHRAE Journal - September 2009 - 32b
ASHRAE Journal - September 2009 - 33
ASHRAE Journal - September 2009 - 34
ASHRAE Journal - September 2009 - 35
ASHRAE Journal - September 2009 - 36
ASHRAE Journal - September 2009 - 37
ASHRAE Journal - September 2009 - Lab for Learning
ASHRAE Journal - September 2009 - 39
ASHRAE Journal - September 2009 - 40
ASHRAE Journal - September 2009 - 41
ASHRAE Journal - September 2009 - 42
ASHRAE Journal - September 2009 - 43
ASHRAE Journal - September 2009 - Solar Hot-Water Heating System: Lessons Learned
ASHRAE Journal - September 2009 - 45
ASHRAE Journal - September 2009 - 46
ASHRAE Journal - September 2009 - 47
ASHRAE Journal - September 2009 - 48
ASHRAE Journal - September 2009 - 49
ASHRAE Journal - September 2009 - 50
ASHRAE Journal - September 2009 - 51
ASHRAE Journal - September 2009 - 52
ASHRAE Journal - September 2009 - 53
ASHRAE Journal - September 2009 - 50th Anniversary—Low Pressure Steam Heating Systems
ASHRAE Journal - September 2009 - 55
ASHRAE Journal - September 2009 - 56
ASHRAE Journal - September 2009 - 57
ASHRAE Journal - September 2009 - 58
ASHRAE Journal - September 2009 - 59
ASHRAE Journal - September 2009 - 60
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ASHRAE Journal - September 2009 - 69
ASHRAE Journal - September 2009 - 70
ASHRAE Journal - September 2009 - 71
ASHRAE Journal - September 2009 - Building Sciences
ASHRAE Journal - September 2009 - 73
ASHRAE Journal - September 2009 - 74
ASHRAE Journal - September 2009 - 75
ASHRAE Journal - September 2009 - 76
ASHRAE Journal - September 2009 - 77
ASHRAE Journal - September 2009 - 78
ASHRAE Journal - September 2009 - 79
ASHRAE Journal - September 2009 - 80
ASHRAE Journal - September 2009 - 81
ASHRAE Journal - September 2009 - Products
ASHRAE Journal - September 2009 - 83
ASHRAE Journal - September 2009 - Emerging Technologies
ASHRAE Journal - September 2009 - 85
ASHRAE Journal - September 2009 - 86
ASHRAE Journal - September 2009 - 87
ASHRAE Journal - September 2009 - 88
ASHRAE Journal - September 2009 - 89
ASHRAE Journal - September 2009 - People
ASHRAE Journal - September 2009 - 91
ASHRAE Journal - September 2009 - 92
ASHRAE Journal - September 2009 - Classified Advertising
ASHRAE Journal - September 2009 - 94
ASHRAE Journal - September 2009 - 95
ASHRAE Journal - September 2009 - Advertisers Index
ASHRAE Journal - September 2009 - Cover3
ASHRAE Journal - September 2009 - Cover4
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