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 -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.

You need to evaluate potential for reduction of energy use with p hase change materials Howe would you model phase change materials integrated into building materials?

Example 4 (new): natural ventilation You need to solve energy and airflow Energy Simulation Program Air Flow Program ACH Data: geometry weather materials T wall, T supply, T air,… Flow (ACH), h conv T room

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

Site Energy vs. 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. Site energy (End use) Secondary Energy Primary Energy Site Energy Primary Energy HVAC System HVAC – Heating, Ventilation and Air-Conditioning

Example of Primary and Site Energy Site Energy Intensity by Source Primary Energy Intensity by Source Average Annual Energy Consumption in Commercial Buildings

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.

Electric Energy Generation in Power Plants

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

Example 2 of heat pump primary energy efficiency Gas or Coal or Nuclear Power plant heat 100 kWh EE 36 kWh Transportation losses Building at T=75°F EE 33 kWh Heat pump Heat from air, soil, … (100kWh at T=45°F) COP heat pump = kWh heat 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

U.S. Total Primary Energy Consumption by Source and Sector, All numbers are in quadrillion (10 15 ) of Btu 11.2 Total: 101 x Btu

Use of Electricity by Sector, 2007 Total site use of electricity : 3,923,814 thousand megawatthours ~ 13.3 x Btu For the reference and approximate calculation : 1 Wh of electric energy is ~ 3 Wh of primary energy

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

Building Energy Use and Green House Emission % 18.6% 35.8% 28.1% ~36%

How to calculate carbon saving? Some useful data mission of Carbon Dioxide - CO 2 - when combustion some common fuels are indicated in the table below. Fuel Specific Carbon Content (kg C / kg fuel ) Specific Energy Content (kWh / kg fuel ) Specific CO 2 Emission (kg CO2 / kWh) Coal (bituminous/anthracite) Gasoline Light Oil Diesel Liquid Petroleum Gas Natural Gas, Methane …. 1) Commonly viewed as a Bio fuel Emission of Carbon Dioxide - CO2 – per unit of energy obtained from different types of fuel.

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

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