David E. Claridge Director Energy Systems Laboratory ... · PDF fileDavid E. Claridge Director...
Transcript of David E. Claridge Director Energy Systems Laboratory ... · PDF fileDavid E. Claridge Director...
David E. Claridge Director
Energy Systems Laboratory Texas A&M University System
Emerging Technologies Summit Sacramento, California
November 8‐9, 2010
ACKNOWLEDGEMENT
Oleksandr Tanskyi performed some of the calculations and prepared some of the initial slides for the work presented here.
BACKGROUND
Reversible Thermodynamics Adiabatic Devices Carnot Cycles/Carnot COP
All Provide Useful Guidance
NEW HOME OF ESL 25,774 FT2
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
ESL OFFICE BUILDING ASSUMPTIONS
Comfort – Maintain 73ºF/50% Relative Humidity Ventilation – Meet ASHRAE Standard 62‐2007
5 cfm/person + 0.06cfm/ft2
Lighting –IESNA recommended levels Computers – 1/person Monitors – 2/person (23‐inch) Printers – 1/person (2000 pages/yr)
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
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?
EXPLORING THE LIMITS:
LIGHTING Chose average of IESNA recommended 20‐50 fc Assume
400 – 700 nM radiation from 5800K black body ~250 Lumens/Watt On 6 hr/day weekdays
LED LIGHTS
EXPLORING THE LIMITS:
LIGHTING 35 fc => 0.13 W/ft2 average occupied hours
Occupancy sensors => 0.01 W/ft2 unoccupied 1.7 kW occupied without daylighting 0.85 kW occupied with daylighting 0.24 kW unoccupied
EXPLORING THE LIMITS:
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
EXPLORING THE LIMITS: MONITORS
Assume limit is lighting power Two 0.14m2 (23‐in) monitors per person 250cd/m2@250Lm/W=> 1.75 W/monitor Sleep when not active 6 hr/day for 256 monitors 206 W average when occupied
EXPLORING THE LIMITS:
PRINTERS
Physical limit not obvious Ink jet printer is ~0.07 Wh/page 2000 pages per person/year => 7 W average when occupied
EXPLORING THE LIMITS: COPIERS
2,000 copies per person per year at ESL Use same energy assumptions as printer 7 W average when occupied
EXPLORING THE LIMITS: COOLED DRINKING WATER
1 qt/day per person from 70ºF to 50ºF Use Carnot refrigerator COPCarnot = 28.3 => 4.3 W average for building (when occupied)
EXPLORING THE LIMITS: HEATING FOOD/WATER
Assume 1 cup water or equivalent food per person daily from 70ºF to 212ºF
Assume Carnot heat pump COPCarnot = 4.66 for 70ºF to 212ºF => 53 W average for building (when occupied)
EXPLORING THE LIMITS: HEATING WATER - RESTROOMS
Assume ½ gal/person per day 70ºF to 105ºF Assume Carnot heat pump COPCarnot = 15.65 for 70ºF to 105ºF => 31 W average for building (when occupied)
EXPLORING THE LIMITS COOLING AND HEATING
Loads Internal Gains Occupants Solar Ventilation Envelope
EXPLORING THE LIMITS: INTERNAL GAINS
Source Occupied (W)
Unoccupied (W)
Lighting 838 240 Computers 147 0 Monitors 206 0 Printers/Copiers 14 0 Water Cooling 4.3 0 Heating Food 53 0 Restroom HW 31 0 Total 1,293 240
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
EXPLORING THE LIMITS: SOLAR GAINS
Theoretical limit is zero We assume the amount of solar gain corresponding to the amount of daylighting
=> 850 W average occupied gain
EXPLORING THE LIMITS:
VENTILATION ENERGY ASHRAE Standard 62‐2004 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
EXPLORING THE LIMITS: ENVELOPE GAINS/LOSSES
Theoretical limit is zero We assume zero
EXPLORING THE LIMITS: COOLING AND HEATING
Assume: “Economizer” cooling when conditions permit Carnot Chiller for cooling otherwise Carnot heat pump for heating
EXPLORING THE LIMITS: 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
EXPLORING THE LIMITS: 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
EXPLORING THE LIMITS: HEATING
Heating Load is zero Heating electricity is 0 kWh!
ELECTRICITY CONSUMPTION: THEORETICALLY POSSIBLE
5,528 kWh 15 kWh
0 kWh
250 kWh
0 kWh
HOW DO TODAY’S BUILDINGS COMPARE?
U.S. Office Building average is 82 kBtu/ft2‐yr site A very good new office building is 12 kBtu/ft2‐yr Theoretically possible 5,528 kWh => 0.73 kBtu/ft2‐yr 0.21 kWh/ft2‐yr!!!
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 ft2 of PV cells would make the 25,774 ft2 ESL office building NET ZERO!