Difference between revisions of "Green Garage Solar Heating Design"

From Green Garage Detroit
Jump to: navigation, search
(Demand Requirements)
(Solar Thermal Collectors)
Line 23: Line 23:
 
** where Heat Output (Q-out) = Temp Rise x Volume Flow Rate x Specific Heat of Water  
 
** where Heat Output (Q-out) = Temp Rise x Volume Flow Rate x Specific Heat of Water  
 
* '''Basics Guidelines'''
 
* '''Basics Guidelines'''
** Solar thermal (liquid) panels are up to 80% efficient ... 5 to 10 times that of PV panels
+
** Solar thermal (liquid) panels are up to 80% efficient ... 5 to 10 times that of PV panels (AR: I would suggest thermal is normally more like 35% to 70% efficient and about 3 or 4 times the efficiency of PV)
 
** The efficiency varies greatly with delta T (Tin - Tout)the greater the difference the lower the efficiency
 
** The efficiency varies greatly with delta T (Tin - Tout)the greater the difference the lower the efficiency
 
* '''Solar Collectors'''
 
* '''Solar Collectors'''
 
** Flat Panel vs. Evacuated Tube
 
** 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
+
*** 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 (AR: I second most of the above, except square foot cost of discount Chinese evacs can be roughly equal to flat plates.)
 
** Manufacturer [[Image:SRCC Data - SunEarth Empire 4x10.png|thumb|100px|SRCC Data for SunEarth  - Empire]]
 
** Manufacturer [[Image:SRCC Data - SunEarth Empire 4x10.png|thumb|100px|SRCC Data for SunEarth  - Empire]]
 
*** [http://www.sunearthinc.com/ Sun Earth]
 
*** [http://www.sunearthinc.com/ Sun Earth]
 
**** [http://www.sunearthinc.com/empire_series_flat_plate.htm Empire Flat Plate] and [http://www.sunearthinc.com/empire.pdf Spec] single glazed, copper, selective absorber |Intercept: 0.758, Slope: -0.727
 
**** [http://www.sunearthinc.com/empire_series_flat_plate.htm Empire Flat Plate] and [http://www.sunearthinc.com/empire.pdf Spec] single glazed, copper, selective absorber |Intercept: 0.758, Slope: -0.727
 
**** [[Conversation with Bob at SunEarth on March 23, 2008]]
 
**** [[Conversation with Bob at SunEarth on March 23, 2008]]
*** Others: [http://solarhotusa.com/index.html Solar Hot Panels] highly recommended, AET (STSS recommended), Solar Thermal System, Heliodyne large market share.  [http://www.apricus.com/ Apricus] ... the evacuated version that Roman used.
+
*** Others: [http://solarhotusa.com/index.html Solar Hot Panels] highly recommended, AET (STSS recommended), Solar Thermal System, Heliodyne large market share.  [http://www.apricus.com/ Apricus] ... the evacuated version that Roman used. (AR: We are now shifting from SolarHot collectors to Solene Cromagen - slightly better numbers and equally good pricing - just under $800 for a 4x10)
 
* '''Preliminary Specifications'''
 
* '''Preliminary Specifications'''
 
** Size: 4ft x 10ft
 
** Size: 4ft x 10ft
Line 38: Line 38:
 
** Positioning
 
** Positioning
 
*** On the annex building flat roof
 
*** 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
+
*** Vertical Angle: 55 degrees per SRCC guide the panels should be (Latitude + 15 degrees) for winter heating driven systems (AR: 10 panels at 55 degrees will probably create a lot of summer overheating.  My first thought for this application is more like 65 to 70 degrees) 
*** 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 [http://aa.usno.navy.mil/cgi-bin/aa_rstablew.pl sunrise/sunset data]
+
*** 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 [http://aa.usno.navy.mil/cgi-bin/aa_rstablew.pl sunrise/sunset data] (AR: I would recommend 5 or 8 degrees West of due South to slightly favor the afternoon sun when it is warmer with lower delta T)
 
*** Configuring
 
*** Configuring
**** Portrait orientation
+
**** Portrait orientation  
**** Parallel connection
+
**** Parallel connection (AR: For lowest cost installation, and best efficiency with least exterior piping, I would recommend all 10 panels in one straight row, in series - Feed emerges from roof at one end. Return enters roof at other end - could not be more efficient) 
**** One feeder pipe to two groups of five panels in parellel (i.e. five per manifold.)
+
**** One feeder pipe to two groups of five panels in parellel (i.e. five per manifold.) ** Thermal Capacity:
** Thermal Capacity:
+
*** 23 Million BTU per heating season (Nov15 - Mar 15) See [http://spreadsheets.google.com/ccc?key=poIdcdytevB8h_kYqyV41EA&hl=en GG Solar Thermal Workbook] (AR: Kudos if you can achieve this - I will take your word for it that you can.)
*** 23 Million BTU per heating season (Nov15 - Mar 15) See [http://spreadsheets.google.com/ccc?key=poIdcdytevB8h_kYqyV41EA&hl=en GG Solar Thermal Workbook]  
+
 
*** [http://www.sunearthinc.com/empire.pdf SunEarth Thermal Capacity]
 
*** [http://www.sunearthinc.com/empire.pdf SunEarth Thermal Capacity]
 
*** Assume
 
*** Assume
Line 51: Line 50:
 
**** Partly Sunny: 560 BTU/sf Winter; BTU/sf Summer
 
**** Partly Sunny: 560 BTU/sf Winter; BTU/sf Summer
 
**** Cloudy: 375 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  
+
** Flow Rate: 1g/m per panel (12 g/m max): Total 10g/m...max at 30 - 40g/min (AR: When you are dealing with a drainback with no heat exchanger on the solar loop side, I feel .5 gpm/collector is adequate.  I feel a full 1 gpm is wasting watts and adding wear and tear on the copper collector piping)
** Pressure: 160 psi
+
** Pressure: 160 psi (AR: What is this? Max. test pressure?  With drainback it is at atmospheric pressure +/-.  With glycol, probably 15 to 25 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  
+
** Temp:  15 - 25F delta T for T in vs. T out; (AR: You will probably find your T in vs. T out is under 15 especially if you have more than about .6 gpm/collector.)  Max - can boil...control with the flow.  Min: - above storage temp or radiant floor or indoor temp  
*** Overheating / Heat dump
+
*** Overheating / Heat dump (AR: If you use a drainback, you have a little more leeway to handle occasional stagnations (no glycol to turn acidic), but I would still recommend some overheat protection - could be a good greenhouse/tarp-roll arrangement manually raised and lowered over part of the array - or a heat dump of some sort.) 
 
***** He has covered the panels...often recommends doing so
 
***** He has covered the panels...often recommends doing so
***** paint the panels with poster paint that washes off  
+
***** paint the panels with poster paint that washes off (AR: Of the 3, I would have least confidence in this measure)
 
***** uses radiator coils with fans to dump heat  
 
***** uses radiator coils with fans to dump heat  
 
* '''Open Issues'''
 
* '''Open Issues'''
** Drainback option that eliminates glycol
+
** Drainback option that eliminates glycol (AR: If possible, and I think it is, I would recommend drainback.)
 
** Thermal capacity calcs...w/ domestic hot water...how many additional panels 2 vs. 3.
 
** Thermal capacity calcs...w/ domestic hot water...how many additional panels 2 vs. 3.
 
** Review other panel manufacturers
 
** Review other panel manufacturers

Revision as of 22:28, 30 March 2009

return to Solar Heating Design

Demand Requirements

  • Load Requirements / Assumptions
    • Targeting meeting 90% of space heating load
    • Design Heating Season = Nov 15 - March 15

AR: This is pretty radical to get to Nov.15 with no heat, but reportedly this was well calculated with super insulation.

    • Total Solar Heating Load = Space Heating Load + Domestic Hot Water
      • Space Heating Load = 22 million BTU per heating season; 184k BTU/day

AR: Again, by normal standards this is at least an order of magnitude low, but ...

Solar Heating System Overview

Green garage Solar Heating Schematic - V5


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 (AR: I would suggest thermal is normally more like 35% to 70% efficient and about 3 or 4 times the efficiency of PV)
    • 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 (AR: I second most of the above, except square foot cost of discount Chinese evacs can be roughly equal to flat plates.)
    • Manufacturer
      SRCC Data for SunEarth - Empire
  • 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 (AR: 10 panels at 55 degrees will probably create a lot of summer overheating. My first thought for this application is more like 65 to 70 degrees)
      • 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 (AR: I would recommend 5 or 8 degrees West of due South to slightly favor the afternoon sun when it is warmer with lower delta T)
      • Configuring
        • Portrait orientation
        • Parallel connection (AR: For lowest cost installation, and best efficiency with least exterior piping, I would recommend all 10 panels in one straight row, in series - Feed emerges from roof at one end. Return enters roof at other end - could not be more efficient)
        • One feeder pipe to two groups of five panels in parellel (i.e. five per manifold.) ** Thermal Capacity:
      • 23 Million BTU per heating season (Nov15 - Mar 15) See GG Solar Thermal Workbook (AR: Kudos if you can achieve this - I will take your word for it that you can.)
      • 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 (AR: When you are dealing with a drainback with no heat exchanger on the solar loop side, I feel .5 gpm/collector is adequate. I feel a full 1 gpm is wasting watts and adding wear and tear on the copper collector piping)
    • Pressure: 160 psi (AR: What is this? Max. test pressure? With drainback it is at atmospheric pressure +/-. With glycol, probably 15 to 25 psi.)
    • Temp: 15 - 25F delta T for T in vs. T out; (AR: You will probably find your T in vs. T out is under 15 especially if you have more than about .6 gpm/collector.) Max - can boil...control with the flow. Min: - above storage temp or radiant floor or indoor temp
      • Overheating / Heat dump (AR: If you use a drainback, you have a little more leeway to handle occasional stagnations (no glycol to turn acidic), but I would still recommend some overheat protection - could be a good greenhouse/tarp-roll arrangement manually raised and lowered over part of the array - or a heat dump of some sort.)
          • He has covered the panels...often recommends doing so
          • paint the panels with poster paint that washes off (AR: Of the 3, I would have least confidence in this measure)
          • uses radiator coils with fans to dump heat
  • Open Issues
    • Drainback option that eliminates glycol (AR: If possible, and I think it is, I would recommend drainback.)
    • Thermal capacity calcs...w/ domestic hot water...how many additional panels 2 vs. 3.
    • Review other panel manufacturers
    • Insulation of panels?

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
  • Preliminary Specifications
    • Location of Storage
      • Ground floor slab in addition bldg
      • Create insulated room w/ R-25 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 radiant heat and domestic hot water) can draw heat from storage via heat exchangers.
    • Size of storage
      • Store 2 million BTU to start (3,500 gallons)
      • Number of tanks: 1 - 3,500 gal
      • Assume 1,500 gal
    • Size: 3,500 gal = 10 ft dia x 7ft tall
    • Capacity: 470cf
    • Thermal Capacity:
      • Winter: 3500 gals = 470cf = 2.3 mBTU: equivalent to approx 13 average winter days (almost two weeks)
      • Summer: TBD
    • 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
  • Open Issues
    • Number of tanks...prefer 1 tank due to cost of heat exchangers
    • 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
  • 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
  • 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
  • Open Issues
    • Normal operating temps winter...summer? Winter = 90F max...summer = 68F min
    • Can radiant floor be used for cooling? Yes see ASHRAE report ... min 68 degrees
    • Plex sizing in Michigan code? Appears we can use 3/4"...1/2 min

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