Green Garage Solar Heating Design
From Green Garage Detroit
return to Solar Heating Design
Contents
Demand Requirements
- See our GG Solar Thermal Workbook
- Load Requirements / Assumptions
- Targeting meeting 90% of heating load
- Design Heating Season = Nov 15 - March 15
- Heating Load = Space Heating Load + Domestic Hot Water
- Space Heating Load = 22 million BTU per heating season; 184k BTU/day
- Domestic Hot Water Load = 120 gals / day
Solar Thermal Collectors
- Goal = highest Heat Output / Total Life-cycle Cost
- Should BTU generated per dollar invested...why not just buy little more of a slightly lower efficient panel that is much less expensive and get same total energy.
- where Heat Output (Q-out) = Temp Rise x Volume Flow Rate x Specific Heat of Water
- Basics Guidelines
- Solar thermal (liquid) panels are up to 80% efficient ... 5 to 10 times that of PV panels
- The efficiency varies greatly with delta T (Tin - Tout)the greater the difference the lower the efficiency
- Solar Collectors
- Flat Panel vs. Evacuated Tube
- Choose: Flat panel because of lower cost (approx 1/3 the cost) and higher durability (twice the life)..performance usually better in the system vs. on the testing bench
- Manufacturer
- Sun Earth
- Empire Flat Plate and Spec single glazed, copper, selective absorber |Intercept: 0.758, Slope: -0.727
- Conversation with Bob at SunEarth on March 23, 2008
- Others: Solar Hot Panels highly recommended, AET (STSS recommended), Solar Thermal System, Heliodyne large market share. Apricus ... the evacuated version that Roman used.
- Sun Earth
- Flat Panel vs. Evacuated Tube
- Preliminary Specifications
- Size: 4ft x 10ft
- Number: 10 = area 400sf
- Positioning
- On the annex building flat roof
- Vertical Angle: 55 degrees per SRCC guide the panels should be (Latitude + 15 degrees) for winter heating driven systems
- Horizontal Angle: solar "true" south - determine at site...slightly west of magnetic south...estimated to be approx + 4degrees degrees for Detroit. +/- 15 degrees is ok. Site for sunrise/sunset data
- Configuring
- Portrait orientation
- Two groups of five panels (i.e. five per manifold.)
- Thermal Capacity:
- 23 Million BTU per heating season (Nov15 - Mar 15) See GG Solar Thermal Workbook
- SunEarth Thermal Capacity
- Assume
- Full Sun: 750 BTU/sf Winter; BTU/sf Summer
- Partly Sunny: 560 BTU/sf Winter; BTU/sf Summer
- Cloudy: 375 BTU/sf Winter; BTU/sf Summer
- Flow Rate: 1g/m per panel (12 g/m max): Total 10g/m...max at 30 - 40g/min
- Pressure: 160 psi
- Temp: 15 - 25F delta T for T in vs. T out; Max - can boil...control with the flow. Min: - above storage temp or radiant floor or indoor temp
- Overheating / Heat dump
- He has covered the panels...often recommends doing so
- paint the panels with poster paint that washes off
- uses radiator coils with fans to dump heat
- Overheating / Heat dump
- Open Issues
- Thermal capacity calcs
- Review other manufacturers
Thermal Storage
- Demand Requirements
- Space heating and domestic hot water. We're investigating cooling ideas.
- Goal is, practically speaking, 90% with a retro fit...no opportunity for below floor storage.
- 10 gallons ( or approx 1 cu ft) for every 1 sf of solar panel if you want to get to near 95% of heating demand
- Hold four days of heat (Rushforth LLC uses 2+ days... and gets much better results than one day)
- Basic Guidelines
- Place storage indoors...not outdoors, because heat loss indoors helps heat the building.
- Manufacturer
- STSS
- Other:
- American Solar Solutions Comes on a pallet and you assemble...you can get it in the basement. Comes in 800 gallon tanks with heat exchangers.
- Design Tank Fiberglass tanks comes in sections
- Preliminary Specifications
- Location of Storage
- Basement on south end: 18' wide x 20' long x 10' high
- Create insulated room w/ R-45 walls + R-25 floor + R-25 ceiling
- Thermal Architecture
- All heat generators (i.e. solar and geothermal) connected to the storage
- All heat consumers (i.e radient heat and domestic hot water) can draw heat from storage via heat exchangers.
- Size of storage
- Store 2 million BTU to start (3,000 gallons) (note: if we can find an affordable 4,000 gal answer that would be great.)
- Number of tanks: 1 (3,000 gal) or 2 (1,500 gal)
- Assume 1,500 gal
- Size: 1,500gal = 6.5ft dia x 6ft tall
- Number: 2
- Capacity: 400cf
- Thermal Capacity:
- Winter: 3000 gals = 400sf = 2 mBTU: equivalent to 11 average winter days
- Summer:
- Thermal Loss: R-19 around tank
- Flow Rate: Max 15g/m ... geothermal connection
- Pressure: Sealed, non-pressurized
- Fluid: Water...no additive
- Temp: Max: 175F Min: above radiant floor or indoor temp
- Location of Storage
- Open Issues
- Number of tanks?
- Min temp from a systems design standpoint...not a tank material standpoint?
- What about using it for off-peak cooling storage for the geothermal?
Radiant Floor
- Demand Requirements
- Areas: 8200sf Historic, 2xxx Annex
- See peak load in GG Solar Thermal Workbook
- Basic Guidelines
- Only 10% of heat is lost through the floor...42% through the roof
- Radiant heats up to about 7ft from the floor
- Manufacturer
- Radiantec from Vermont
- Others:
- Preliminary Specification
- Zones: approx 1100sf; 8 - Historic; 2 - Annex
- Circuits: 6 per zone
- Plex: 1/2in
- Spacing: 8in
- Flow Rate: 4.5 g/m
- Temp: normal winter operating 90F; max = 130F
- Thermal Capacity: 38,000 BTU/hr per zone
- Floor architecture
- Historic
- Vapor barrier or sealer (10mm?)
- Two layers of 1" XPS with seams staggered and sealed. (2")
- Reflective radiant barrier (could be foil on the XPS?) (mm)
- Sleepers (1.5") with metal heat extenders
- Plywood? Wood Flooring (1")
- All screwed together, run trenches
- Historic
- Open Issues
- Normal operating temps winter...summer?
- Can radiant floor be used for cooling?
- Plex sizing in Michigan code?
Geothermal
- Preliminary Spec
- Location: Basement
- Connect Geothermal to with open loop to the mass storage
- Manufacturer
- Water Furnace...Envision
- Open Issues
- Geothermal - operating temps (min-max)
Resources
- Overall
- Overall Concept ... recommends thermal storage.
- DOE Solar Liquid Heating
- Solar Thermal System Calculator Surpisingly sophisticated
- Natural Sun Heating - Mentor is Sunpower Designs from Laren Corie
- Build it Solar - wonderful resource for everything solar
- Dr. Shurcliff's 101 Solar Space Heating designs excellent common sense ideas for solar heating
- Passive ZED/Solar Heating Site
- Rushforth Solar LLC Solid consulting company in PA for solar heating.
- The Oil Drum forum