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Lecture Objectives:

Lecture Objectives:. Finish with example modeling problems Phase change thermal storage materials Energy and airflow Interpret energy simulation results. Example 3 from previous class: Phase change materials. Next generation of energy efficient building materials

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Lecture Objectives:

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  1. Lecture Objectives: • Finish with example modeling problems • Phase change thermal storage materials • Energy and airflow • Interpret energy simulation results

  2. Example 3 from previous class: Phase change materials • Next generation of energy efficient building materials • Integrate phase change materials (PCMs) to insulation • Reduce peak heat transfer rates across walls and ceilings, • Shift peak cooling loads and reduce size of equipment, • Large potential for reduction of energy use, • Use nanotechnology, • Can be used in insulation or any other building material.

  3. You need to evaluatepotential for reduction of energy usewith phase change materials • Howe would you model phase change materials integrated into building materials?

  4. Energy Simulation Program Air Flow Program Example 4 (new):natural ventilation You need to solve energy and airflow Twall,Tsupply,Tair,… ACH Data: geometry weather materials T room Flow (ACH), hconv

  5. What are the reasons for the energy simulation? • Design (sizing of different systems) • Economic benefits • Impact on environed • Fuel budget planning

  6. Site Energy vs. Primary Energy Primary Energy Site (End-use)energy is the energy directly consumed by end users. Secondary energy is site energy plus the energy consumed in the production and delivery of energy products Primary energy is site energy plus the energy consumed in the production and delivery of energy products. Secondary Energy HVAC System Site energy (End use) HVAC – Heating, Ventilation and Air-Conditioning Site Energy Primary Energy

  7. Example of Primary and Site Energy Average Annual Energy Consumption in Commercial Buildings Primary Energy Intensity by Source Site Energy Intensity by Source http://www.eia.doe.gov/emeu/consumptionbriefs/cbecs/cbecs_trends/intensity.html

  8. Site Energy vs. Primary Energy • Electricity, of the major energy sources, has the greatest disparity between site and primary energy. • Greater amount of energy is used to generate and transmit electricity than in the production and distribution of the other major sources. • In 1995, steam-electric utility plants were estimated to have used 10,301 Btu of fossil-fuel energy to generate 1 kilowatthour of electricity. • i.e., approximately 3.02 Btu of fossil-fuel energy were used to generate 1 Btu of electricity.

  9. Electric Energy Generationin Power Plants

  10. Example 1 of primary energy usefurnace v.s. energy efficiency Gas furnace Furnace (80% efficient) 100 kWh ~79 kWh 95 kWh heat Chemical energy Chemical energy Transportation losses Gas Overall efficiency 79% Electric heater Electric Heater (100% efficient) 100 kWh 33 kWh 36 kWh 33 kWh Power plant heat EE EE heat Transportation losses Gas or Coal or Nuclear Overall efficiency 33%

  11. Example 2 of heat pump primary energy efficiency COP heat pump = 4 Building at T=75°F Heat pump 100 kWh 133 kWh 36 kWh 33 kWh Power plant heat EE EE heat Transportation losses Gas or Coal or Nuclear Heat from air, soil, … (100kWh at T=45°F) Overall efficiency 133% However, what is the exact saving? how much will it cost? what kind of system wee need? can we use this system everywhere? …. Energy modeling and life cycle cost analysis

  12. U.S. Total Primary Energy Consumption by Source and Sector, 2007 All numbers are in quadrillion (1015) of Btu 11.2 29.4 Total: 101 x 1015 Btu http://www.eia.doe.gov/emeu/aer/pecss_diagram.html

  13. Use of Electricity by Sector, 2007 For the reference and approximate calculation : 1 Wh of electric energy is ~ 3 Wh of primary energy

  14. Do we need stronger motivation to improve our buildings and building systems? Total Primary Energy Consumption by Source and Sector, 2007 • Total primary energy: 101.4 x 1015 Btu • ( 29,700,000 thousand MWh) ~ 21% residential ~ 18% commercial

  15. Building Energy Use and Green House Emission ~36% 17.5% 18.6% 35.8% 28.1% http://www.eia.doe.gov/oiaf/1605/ggrpt/index.html http://www.eia.doe.gov/oiaf/1605/ggrpt/flowchart.html

  16. mission of Carbon Dioxide - CO2 - when combustion some common fuels are indicated in the table below. How to calculate carbon saving? Some useful data Emission of Carbon Dioxide - CO2 – per unit of energy obtained from different types of fuel. 1) Commonly viewed as a Bio fuel

  17. Zero Energy House High Tech - Solar Decathlon Competition UT at Austin Promote development of solar technology and energy efficient building systems Residential Buildings Technische Universität Darmstadt Cost of these prototype houses: from 200$/sf to 1000$/sf

  18. Low Energy Sustainable Houses Low Tech Green roofs Straw bale house Integration of various solutions Nice examples of sustainable houses, but…. Can you use this technology here and if yes how large is the overall impact Mexico City New York

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