Solar Water Heating on StFX Campus Final Presentation Meghan Hanington, Alexander MacDonald, Blake Meech, Connor Hanna & Alex MacDonald

Outline Background Information Domestic hot water & Current Process Solar Water Heating Design Description System overview & Requirements Components & Drawings Analysis Structural Analysis & System performance Cost Analysis System limitations

Domestic Hot Water Domestic hot water is hot water that is used within a building for showering, cooking or cleaning A typical system takes water from a central water supply and uses electricity or burns a fossil fuel to generate heat in a boiler Heat is transferred to the water supply and the water temperature rises Trim?

Problem On StFX campus, domestic hot water is heated using steam that is generated in the Central Heating Plant using Bunker B fuel and fish oil. Overall efficiency around 69% Burning bunker fuel produces greenhouse gases and may not be sustainable Fuel must be shipped from Quebec 3 times per week which further increases the associated costs and carbon emissions Source: [1]

Project Site MacIsaac Hall Building has large south-facing flat and sloped roof sections suitable for solar water heating Buildings mechanical room and washrooms are located directly under the flat roof section Estimated daily hot water demand of 17550 L

Project Goals Determine the available MacIsaac Hall roof area and increased load on the roof from the solar collectors Identify the methods for integrating the solar water to the existing steam system to properly preheat water Determine the proper equipment necessary in order to ensure the SWH system works correctly and safely Analyze the performance of the SWH system and provide estimates on energy output Conduct a cost and environmental analysis on the project to determine its feasibility and benefits

What is Solar Water Heating? Solar water heating involves converting energy from the sun into heat for water heating. Wide variety of system types Direct and indirect Active and passive Source: [2]

Direct or Indirect? Active or Passive? Closed loop piping Heat transfer fluid transfers heat absorbed in the solar collectors to the domestic water supply Direct Directly heat water Prone to freezing in cold climates Active Pumps and controllers circulate the working fluid from collectors to the storage tank Passive No pumps Less control over flow of fluid MacIsaac Hall site will be indirect and active Full control over fluid and protection from freezing Trim?

System Overview Flowchart

Design Requirements Produce energy for all months of occupancy in MacIsaac Hall 100% powered by renewable energy Have a fail-safe control system to protect the glycol fluid and optimize energy production. Integrate with the current steam based hot water generation system Provide energy storage to ensure energy is not wasted during peak production.

Required Equipment Solar collectors Solar pump PV solar panels Temperature sensors and a solar controller Glycol working fluid Storage tank with a heat exchanger Drain back tank Piping Wiring Frame and mounting rods Source: [2]

Location of Installation On the flat and sloped roof sections directly above MacIsaac Hall’s mechanical room System complexity can be reduced Pipes can travel from the roof directly to the mechanical room through a nearby existing chimney chute that is currently not in use The existing steam hot water heater is located in this mechanical room and there is available space for a storage and drain back tank The available roof space was found using AutoCAD files for the building provided by Kevin Latimer 20 Thermo-Dynamics Ltd. G Series solar collectors could fit in this area

Location of Installation

G Series Solar Collectors Produced by Thermo Dynamics Ltd. Design life of 35 years Flat plate type mounted on a lightweight aluminum frame Can withstand very high operating temperatures and pressures Can be arranged in an array of any size Installed on flat roof at 37 degrees Optimal angle depends on latitude [3] Installed on sloped roof at 27 degrees

Shadow Calculation Maximum shadow for the collectors mounted on the flat roof Source [4] Trim?

Collector Performance Maximum ideal efficiency for the G Series solar collectors is 0.689 [2] Converting solar radiation to energy stored in the glycol solution The angle of inclination, position in relation to the sun, geographical location and weather influence the solar collector efficiency To estimate an actual efficiency for the panels, the software RETScreen was used and an efficiency of 0.55 was calculated. In knowing the efficiency and daily averages for solar radiation we can calculate the potential energy output for the total array of solar collectors

Example Calculation Energy production for a typical day in January

Solar Pump Powered by small, 20W solar panels Connected to temperature sensors that will signal to turn the pump on or off. For drain back systems, Thermo Dynamics recommends a system operating pressure below 30 psi (206843 Pa) Can determine the proper capacity to meet the requirements for flow rate and pump head

Pump Calculations 3 parallel sets of collectors connected in series Each set has maximum flow rate of 1.5 L/min for at total of 4.5 L/min Required pump head can be calculated The solar pumps available from Thermo Dynamics all produce up to 35m of head (different flow rate capacities) If a design pressure of 20 psi (138 000 Pa) is chosen, the required pump head becomes 32m Direct-Drive Solar Pump (P118330) was selected Can easily handle the flow rate requirement of 4.5 L/min

Pump Calculations Cont.

Control System Involves the solar pump, temperature sensors and a drain back tank Three temperature sensors should be used Solar pump is only activated by the controller when the return line is at a higher temperature than the supply line Controller also has low and high temperature range for the sensors High limit should be set at 90 C and the low limit at -10 C Pump shuts off, glycol flows to drain back tank via gravity

PV Solar Panels The solar pump operates using a 12 volt (DC) supply Power requirement is 35W Two 20W PV modules can be used The approximate length of cable is 20m, connecting the solar controller in the mechanical room to the PV panels on the roof #14 American Wire Gage (AWG) cable is recommended by the manufacturer Has an ampacity rating (maximum current) of 15 Amps [5], so operating at 1.67 Amps is safe

Calculation To supply 20W of power at 12 volts, the current requirement will be 1.67 Amps

Piping and Wiring Piping 3/4’’ unions for tanks and solar collectors 3/4’’ copper pipe is sold by 50’ lengths Insulation is sold per 6’ Total length estimate is 131m Wiring PV and sensor wire is #14 AWG Sold per 1’ Total length estimate of 25m

Heat Transfer Fluid Propylene Glycol is a chemical commonly used in heat transfer applications Has a wide operating temperature range Used as heat transfer fluid due to its lower freezing temperature Allows the solution to be safe for use in the winter Thermo-Dynamics Ltd. offers two propylene glycol fluids

Advantages to Mixed Glycol Solution The mixed glycol solution has: Cheaper cost Higher specific heat capacity Increased heat transfer capabilities Downside is the higher freezing temperature Antigonish does not regularly reach -24 °C Control system will ensure fluid is protected regardless

Drain Back Tank Protect the system by ensuring that the glycol does not begin to freeze or boil Controlled by the solar pump HTP Drain Back Tank The maximum volume of glycol that could be in our system is 83L HTP Drain Back Tank SSU-20DB Capacity 113L (30 Gallon) Diameter 489mm (19.25 '') Height 990mm (39'') Inlet/Outlet connections 19.05 mm (3/4’’) Cost $905

Hot Water Storage Tank Flexibility in choosing the size and number of hot water storage tanks Hot water demand much greater than production rate An indirect water heater was chosen (closed loop) The glycol solution will be passing through the coil to transfer energy to the water Bradford White Indirect Water Heater (269 L Capacity) Very efficient Minimal stand by heat losses of 1.1C per hour Single Unit, $1500 Hot water stored at max of 71C

Storage Tank Cont Energy capacity Energy demand > Energy production Water stored at 71°C (160°F) Energy demand > Energy production Even if there is no demand, the tank can store energy for 100 minutes of peak production from the collectors

Structural Analysis Statically indeterminate axially loaded member (inclined solar collector) Compatibility equation is to be used for this calculation Determine if the Aluminum 6061-T6 supports at B & C will hold the collectors Given the cross sectional area of the supports from Thermo Dynamics Ltd. manufacturer (square 0.041m x 0.041m)

Structural Analysis Cont Found support reactions from equations (2)-(7) From equation (1) With max winds of 250 km/h winds, the wind force acting on the collector would be, P=8600N Source [6] Max weight of solar collector with glycol fluid, W=450N Solved for critical yield strength in supports from equation (8)

Structural Analysis Cont Flat roof section Sloped roof section

System Performance & Savings Energy production limited by: Collector and heat exchanger efficiency Heat losses in pipes and storage tank

Cost Analysis Cost breakdown Could not obtain an installation quote

Cost Analysis Cont. Two potential project payback periods Just including production in months of occupancy (September to May) Savings of $2000 annually 17 year payback period For full production all year Savings of $3400 annually 10 year payback period

Environmental Analysis System has potential to reduce C02 emissions by 7700 per year by reducing fuel consumption in Central Heating Plant Equivalent to planting 350 trees [7]

Limitations Proposed SWH system will only produce approximately 13% of the total hot water required in MacIsaac Hall during school months Highest energy production occurs when building is empty

Conclusions Proposed SWH system has potential to: Generate 477000 L of hot water in months of occupancy Reduce fuel costs by $2000 annually reduce C02 emissions by 7700 kg per year Be powered 100% by renewable energy Project payback period of 17 years Reduced to 10 years if full year production is met

Recommendations Financing options to reduce project payback period Incentives or grants Look for ways to use energy produced in the summer in other buildings on campus Hot water in other buildings, such as O’Regan & Riley Hall Long term energy storage Possible Geothermal applications To completely replace steam hot water heating in MacIsaac Hall: A larger number of collectors and storage tanks would be required

Project Schedule

Acknowledgements Mr. Kevin Latimer StFX University Facilities Management Dr. Emeka Oguejiofor, FEC, P.Eng. StFX University Mr. Mohammad Azad StFX University Mr. Paul Doiron, P.Eng. A.H. Roy & Associates Mr. Daniel Doiron, P.Eng. A.H. Roy & Associates Mr. Josh Bouchie, P.Eng. A.H. Roy & Associates Mr. Ronald Kell, P.Eng. A.H. Roy & Associates

References Kevin Latimer, FM http://www.thermo-dynamics.com http://www.solarpaneltilt.com https://www.viessmann.ca/content/dam/vi-brands/CA/pdfs/doc/vitosol/vitosol_sdg.pdf/_jcr_content/renditions/original.media_file.inline.file/vitosol_sdg.pdf 2015 Canadian Electrical Code https://www.engineeringtoolbox.com/wind-load-d_1775.html https://projects.ncsu.edu/project/treesofstrength/treefact.htm

Questions?