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Westby-Moss Zero Energy Solar Greenhouse Robert Westby Laboratory Program Manager Federal Energy Management Program NREL Power Lunch Lecture December 4, 2013
Westby-Moss Zero
Energy Solar Greenhouse
Robert Westby Laboratory Program Manager Federal Energy Management Program
NREL Power Lunch Lecture
December 4, 2013
Problem Statement
Design Objective
Design Features Overview
Salient Design Features
Going Forward: Monitoring and Verification
Architect/Energy Designer comment
Contents
Opportunity
Food has a large -and largely wasteful- energy/carbon
footprint (transportation, “field to table”).
Local growing using greenhouses to extend the growing
season helps address this issue.
However, conventional greenhouses typically require
considerable auxiliary heat to keep crops from freezing on cold nights (excessive fenestration, poor insulation and
insufficient thermal mass).
The opportunity is to address these shortcomings with a zero
energy SGH integrated design solution.
Integrated Design Solution Approach
Smart Controls For all sub-system operations
(ventilation, thermal storage, shutters,
CO2 levels, etc.)
Heavy Wall & Roof Insulation:
Minmizes winter-time heat losses;
allows for year-round harvests. PV System (with storage)
meets all electrical needs. High Solar Heat Gain
Glazing & Light Shelves
The design minimizes the
area of windows
needed.
Automated Insulating
Shutters: Reduces heat
loss at night & heat gain
in the summer.
Thermal Mass: Holds
heat & prevents drastic
temperature swings.
Perimeter Foundation Insulation:
Creates a 65º F+ ‘thermal bubble’ for soil temperatures year-round.
Design Objective
Zero energy for all thermal and electric uses while supporting
year-round local growing at 7,800 feet (Proof of Concept)
Design Approach. Based on “alpha” version of design of SGH
located in Boulder, CO which achieved zero energy thermal
performance while supporting year round local growing
(monitored and verified over a full year of operation).
Thermal Energy Performance. Energy engineering assessment:
winter losses = 20MBtu, winter solar gains = 27.6MBtu, 125% of
load. Thermal storage system conservatively sized to offset any
net hourly heat losses.
Electric Energy Performance. Off-grid photovoltaic system sized
conservatively to exceed all electrical loads. Battery storage
capacity facilitates three days + of autonomous SGH operation.
Salient Design Features
Optimized Window Area
Much less glazing then traditional SGH (thermal
management)
Optimized overall window area (0.45:1 window to floor area
ratio)
High solar heat gain coefficient (SHGC=0.69)
High visible light transmittance (VLT=79%)
Conventional greenhouses require
significant auxiliary heat to keep
crops from freezing on cold nights
and to maintain winter growth rates.
Insulated Shutters
All windows and ventilation
openings shuttered (R13)
Automated operation
Microcontroller actuation
Input from solar radiation
and temperature sensors
(solar gain > or < heat loss)
Shutter surfaces reflective
Shutter drive mechanism (low
wattage/12 VDC vehicle window motor)
Thermal Storage System
Ground coupled earth storage (80,000 Btu/F
capacity)
Automated operation (fan operation
controlled by microprocessor/temperature
sensor (internal air temperature controlled:
“charges” > 75F and “discharges” < 45F)
Thermal Storage Soil Temperature Data
Soil Temperature
Sensors/Well
Sensor Well Locations
A
B
C
OUTDOOR INDOOR
Depth/Sensor East Side South Bed North Bed
Surface/To 46.2 72.2 73.3
-1ft./T1 42,7 63.3 64.1
-2ft./T2 45.8 63.1 61.8
-3ft./T3 48.0 58.6 59.5
-4ft./T4 49.7 56.8 58.3
-5ft./T5 51.7 55.0 57.5
Soil Temperature Data (ºF as of 12/01/13)
A B C
“Intelligent Building” Controls
Controls enable autonomous automated
operation of insulated shutters and thermal storage system.
Insulated window shutters actuated by
microcontroller based on input from solar
radiation and temperature sensors (solar
gain > or < heat loss).
Thermal Storage system fan operation
controlled by microprocessor/temperature
sensor (internal air temperature controlled:
“charges” > 75F and “discharges” < 45F).
Ventilation System -
Autonomous/automated control system
under development.
Control box (microcontroller;
shutter, thermal storage and
ventilation system
electronics)
Photovoltaic System
Stand alone 12 VDC system
• 750 watts ((3 Lumos LS250
Watt modules),
• 516 amp hours (Ah) storage
capacity (2 Concord PVX258
Sun Xtender Absorbed Glass
Matt batteries)
• Outback Flexmax 60 charge
controller
• Power Brite APS600 600 watt
inverter for AC powered fans
Electrical Loads
• 120VAC connected: 260
watts (ventilation and thermal
storage fans)
• 12VDC connected: 77 watts
(lighting (LED), shutters,
electronics, etc.)
Increasing Light Availability (Photosynthesis)
Light shelves
• Installed on all south facing windows ( 0.92 reflectance factor)
• Increases sunlight collected by over 25%
• Seasonally adjustable
Highly reflective interior paint
High VLT windows (VLT=0.79)
Reflective insulating shutter surfaces
Performance Monitoring and Verification
M&V Plan Objectives
• Energy performance verification (LBC certification)
• SGH performance and operational R&D
Comprehensive data acquisition system installed (next slide)
• One year period of performance (start September, 2013)
• Measured performance parameters
• Thermal storage ground temperatures (cross section of depths)
Build and calibrate performance models.
• Thermal model (MatLab)
• Daylight model (Radiance)
Develop ventilation system control algorithms.
Data Acquisition System
Sensor Sensor Function
4 Campbell Scientific HMP60 Temperature and relative humidity for the interior, exterior, and
thermal storage intake and exhaust
4 LI-COR Photosensors Light measurements within the greenhouse
1 LI-COR LI90SB Quantum Sensor Measures Photosynthetically active radiation. Located next to
the front light sensor.
1 Magnetic Reed Switch Insulated shutter position
Exhaust and thermal storage fan operation Measure operation of the fans
Omega FTB4605 Irrigation water flow
Vaisala GMW21 Carbon dioxide
Campbell Scientific CS300 Exterior global horizontal irradiance
Architect: Barrett Studio Architects
"One of the things that excited us as architects, was the
notion that growing food, year round, at altitude with only
natural energy input is so challenging, that it calls for very
specific architectural form. In bringing together such a
climatically responsive set of integrated systems, systems
that sense and control light, heat, temperature and
humidity fluctuations, and seasonal variations, form
doesn't only follow function, form literally expresses
function... not stylized or decorated form, but responsive,
unembellished form that is honest and direct. In some
ways, this integrated set of functional sensing systems
mimics living organisms. In this it is an ecomorphic
expression, or what might be termed a Living
Architecture.“
David Barrett, FAIA Barrett Studio Architects
1944 20th St. Boulder, CO 80302 303.449.1141 www.barrettstudio.com
Energy Designer: Synergistic Building Technologies
Next Generation Design Directions
• Further optimization of fenestration area
• High VT, lower cost glazing materials
• Reflective insulating louver systems (RILS)
• Enhanced electronic controls for RILS
• and other shutter systems
•
Design of Next Generation of Zero Energy Greenhouses
Larry Kinney, PhD
President & Chief Technology Officer
Synergistic Building Technologies
1335 Deer Trail Road
Boulder, CO 80302, USA
303-449-7941
www.SynergisticBT.com
LarryK@Synergistic BT.com
