David E. Claridge Director Energy Systems Laboratory Texas A&M University System

Transcription

1 David E. Claridge Director Energy Systems Laboratory Texas A&M University System Emerging Technologies Summit Sacramento, California November 8 9, 2010

2 ACKNOWLEDGEMENT Oleksandr Tanskyi performed some of the calculations and prepared some of the initial slides for the work presented here.

3 BACKGROUND Reversible Thermodynamics Adiabatic Devices Carnot Cycles/Carnot COP All Provide Useful Guidance

4 NEW HOME OF ESL 25,774 FT 2

5 BASIC ESL OFFICE BUILDING REQUIREMENTS Comfort for Occupants Cooling and Heating Ventilation for Indoor Air Quality Lighting Computers/Printers Copiers Cooled Drinking Water Heating Lunch and Coffee Hot Water Restrooms Computer Servers

6 ESL OFFICE BUILDING ASSUMPTIONS Comfort Maintain 73ºF/50% Relative Humidity Ventilation Meet ASHRAE Standard cfm/person cfm/ft 2 Lighting IESNA recommended levels Computers 1/person Monitors 2/person (23 inch) Printers 1/person (2000 pages/yr)

7 ESL OFFICE BUILDING ASSUMPTIONS Copiers 1/30 people (2000 pages/person/yr) Cooled Drinking Water 1qt/person/day Cooled from 70ºF to 50ºF Heating (1 cup water)/person/day Heated from 70ºF to 212ºF Hot Water Restrooms ½ gal/person/day Heated from 70ºF to 105ºF Computer Servers Outsourced Occupied 60 hours/week

8 EXPLORING THE LIMITS What are the limits? What is the minimum energy required to meet each of these office building requirements? What is the minimum energy required to provide these services in our office building?

9 LIGHTING Chose average of IESNA recommended fc Assume nm radiation from 5800K black body ~250 Lumens/Watt On 6 hr/day weekdays LED LIGHTS

10 LIGHTING 35 fc => 0.13 W/ft 2 average occupied hours Occupancy sensors => 0.01 W/ft 2 unoccupied 1.7 kw occupied without daylighting 0.85 kw occupied with daylighting 0.24 kw unoccupied

11 COMPUTERS No obvious physical limit Assume 2.5W for 1 GHz processor (e.g. iphone 4) Hibernate when not in use Assume 30 hr/wk for 128 people => 147 W average when occupied

12 MONITORS Assume limit is lighting power Two 0.14m 2 (23 in) monitors per person 250cd/m 1.75 W/monitor Sleep when not active 6 hr/day for 256 monitors 206 W average when occupied

13 PRINTERS Physical limit not obvious Ink jet printer is ~0.07 Wh/page 2000 pages per person/year => 7 W average when occupied

14 COPIERS 2,000 copies per person per year at ESL Use same energy assumptions as printer 7 W average when occupied

15 COOLED DRINKING WATER 1 qt/day per person from 70ºF to 50ºF Use Carnot refrigerator COP Carnot = 28.3 => 4.3 W average for building (when occupied)

16 HEATING FOOD/WATER Assume 1 cup water or equivalent food per person daily from 70ºF to 212ºF Assume Carnot heat pump COP Carnot = 4.66 for 70ºF to 212ºF => 53 W average for building (when occupied)

17 HEATING WATER - RESTROOMS Assume ½ gal/person per day 70ºF to 105ºF Assume Carnot heat pump COP Carnot = for 70ºF to 105ºF => 31 W average for building (when occupied)

18 Loads Internal Gains Occupants Solar Ventilation Envelope EXPLORING THE LIMITS COOLING AND HEATING

19 Source EXPLORING THE LIMITS: INTERNAL GAINS Occupied (W) Unoccupied (W) Lighting Computers Monitors Printers/Copiers 14 0 Water Cooling Heating Food 53 0 Restroom HW 31 0 Total 1,

20 OCCUPANT GAINS ASHRAE: Moderately active office work: 73 W/person sensible 59 W/person latent Assume 40 hours/week/person => 6,250 W sensible 5,000 W latent

21 SOLAR GAINS Theoretical limit is zero We assume the amount of solar gain corresponding to the amount of daylighting => 850 W average occupied gain

22 VENTILATION ENERGY ASHRAE Standard requires 2190 cfm when occupied Assume 12 hours/day weekdays Perfect enthalpy recovery device Exhaust = outside air intake 5 Pa fan pressurization Perfect fan => 5.1 W fan power when occupied is only ventilation energy required

23 ENVELOPE GAINS/LOSSES Theoretical limit is zero We assume zero

24 COOLING AND HEATING Assume: Economizer cooling when conditions permit Carnot Chiller for cooling otherwise Carnot heat pump for heating

25 COOLING LOADS Gains Occupied (W) Annual Total (kwh) Internal 1,293 3,883 Occupant Sens. 6,250 18,757 Occupant Lat. 5,000 15,006 Solar 838 2,515 Ventilation Load 0 0 Envelope Load 0 0 Total Load 13,371 W 40,161 kwh

26 CHILLER ELECTRICITY Assume Houston, TX Weather Total Cooling Load = 40,161 kwh Economizer meets 24,595 kwh Chiller provides 15,566 kwh Chiller requires 250 kwh Average COP = 62

27 HEATING Heating Load is zero Heating electricity is 0 kwh!

28 ELECTRICITY CONSUMPTION: THEORETICALLY POSSIBLE 0 kwh 15 kwh 5,528 kwh 250 kwh 0 kwh

29 HOW DO TODAY S BUILDINGS COMPARE? U.S. Office Building average is 82 kbtu/ft 2 yr site A very good new office building is 12 kbtu/ft 2 yr Theoretically possible 5,528 kwh => 0.73 kbtu/ft 2 yr 0.21 kwh/ft 2 yr!!!

30 IF WE COULD DO THIS - We could power the U.S. level of office space for every person in the world on 28% of the ELECTRICITY used today in U.S. offices! And 200 ft 2 of PV cells would make the 25,774 ft 2 ESL office building NET ZERO!