Solar Thermal 2011: 10 Steps to Solar Water Hea ng Design
Kurt Koegel Solar Skies Mfg. LLC 320-762-1151 [email protected] Design Typical Commercial Installa on Drainback System
Courtesy of Thelen Hea ng Typical Commercial Installa on Drainback System
Courtesy of Thelen Hea ng Typical Commercial Installa on Drainback System
Courtesy of Thelen Hea ng System Design
When designing a system, the most important part of the design process is understanding.
Determine what the needs are and the possible solu ons, while staying inside predetermined parameters and understanding how each affects the other during the process of design.
Ground Rules of Design
• Keep it simple • Solar is supplemental • Solar is site specific • The system must make sense • Aesthe cs are important, make it look good Site Assessment •A site visit used to verify job site condi ons and dimensions •Extremely important part of design •Can be done before and/or during design process •Take pictures and measurements of everything Design Steps 1. What type of hea ng load is to be supplemented? 2. What type of back up equipment will be used? 3. What type of solar thermal system best es in? 4. How much room available for collectors? 5. How much room available for mechanical equipment? 6. How much of a budget allowed? 7. How much of a load? 8. What type of collectors? 9. What is the frequency of use? 10.How much storage required? System Design; Step 1 Determine what type of hea ng system the solar thermal water hea ng system will be supplemen ng; – Domes c water hea ng – Space hea ng – Combina on system – Cooling – Pool hea ng system – Other System Design: Step 2 Back Up Water Heater Type
Electric water heater • Tank type • Tank less Gas water heater • Tank type • Tank less Indirect water heater – boiler Other System Design: Step 2 cont. Back Up Space Heater Type Boiler • What type of heat convector? • Low temperature (best applica on) – radiant floor • High temperature (worst applica on) – fin tube radiators, cast iron radiators Furnace Heat pump • Air source • Geo thermal Other System Design: Step 3 Solar Loop Type • Closed Loop – Pressurized • Closed Loop – Drain Back • Open loop- Direct system • AC Powered Pump • PV Powered Pump – Direct – With controller System Design: Step 4 Available area for collectors • Shade free, south facing area. – Roof mount – Awning mount – Ground mount • Type of roof covering. – How will penetra ons be water-proofed • Structure – Is it structurally sound enough to mount collectors on – How will collectors be a ached to structure System Design: Step 5 Available area for mechanical equipment • How much room is available in the mechanical room for; – Pumps – Tanks – Piping – Heat exchangers System Design: Step 6 Budget • Is there a set amount available for solar? • Will other factors determine how much is spent on solar? – L.E.E.D. points – Co2 offset – Energy offset – Grants available – Tax incen ves available – Financing availability Budget
• Solar Thermal Cost Rules of Thumb • Water hea ng systems - $100 - $150 per sq. . of collector installed • Pool hea ng systems - $90 - $ 125 per sq. of collector installed
Includes all cost, including labor, materials, engineering, permits, structure, etc.
System Design: Step7 Load
• How much of a load? • How many gallons to be heated? • How much hot water will be used?
Don’t size system off of exis ng equipment capacity The actual number of gallons or btu’s used per day may not be known by owner. A meter may have to be installed to determine actual use. ASHRAE standards can be used as guideline for usage
System Design: Step7 Load calcula on example Amount of Hot Water Needed 4 # of people X 20 20 gal./person/day = 80 gal. hot water/day
Amount of Energy Needed 80 gal. hot water/day X 8.33 lbs. /gal. = 666.4 lbs. of water X 80 ∆ T = 53,312 Btu’s needed System Design: Step 8 What Type of Collectors When the load is determined and during what season it will occur, the collector can be chosen. • What type – Un Glazed – Glazed – Evacuated Tube • What is the performance per dollar • What is the size and weight • Collector angle can be chosen to op mize performance
System Sizing Collector Tilt Rules of Thumb
• Year Round Use – La tude + 0° Domes c Hot Water • Primarily Summer Use – La tude -15° Pool Hea ng • Primarily Winter Use – La tude + 15° Space Hea ng • + or – 15⁰ Tilt Will Not Affect Annual Performance Much Performance vs. Collector Angle
Collector Angle 1.6 30˚
1.4 45˚
60˚ 1.2
1
0.8 Total 12 Month Output (2) SS-32's
Million BTU's Million 0.6 45⁰ N. Lattitude 30˚ = 12.26 MBTU 0.4 45˚ = 12.48 MBTU
0.2 60˚ = 12.02 MBTU
0 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar System Design: Step 9 Frequency Pa erns of load or hot water use – when will it be used • How much per season? • How much per month? • How much per day? • How much per hour?
This will help determine the storage needed. System Design: Step 10 Storage Tank Sizing
Think of a storage tank as a ba ery, it’s a place to store energy for later use.
• If the use is in the evening or early morning, storage should be sized for a full days produc on • If use is during late morning through evening, storage can be downsized.
System Design: Step 10 Storage Tank Sizing guidelines
Try to size storage to achieve best usable temperature in tank For Domes c Hot Water Use 1 to 1.5 Gallons of Storage for Every 1 Sq. Ft. of Collector. For Space Hea ng Use 1-3 Gallon of Storage for Every 1 Sq. Ft. of Collector.
Drainback Tank Sizing Rule of Thumb Tank Should Be About Double The Collector And Piping Volume, Above The Drainback Tank Example (2) 4’x8’ Collectors = 2.1 Gallons 100’ of ¾’’M Copper pipe = 2.7 Gallons 4.8 Gallons x 2 9.6 Gallons Use a 10 Gallon Drainback Tank
System Design Once all parts of the design equa on are determined, the calcula on can begin.
The easiest way is to use a sizing and energy modeling program.
System Design Energy Modeling Programs • Energy modeling programs accurately es mate system performance using local weather data, specific collector performance and balance of system components.
• Most popular – RETScreen – T- Sol – F-Chart
System Design There is no such thing as a dumb ques on, only dumb answers.
Ques ons?
Thank You!
Kurt Koegel Solar Skies Mfg. LLC 320-762-1151 [email protected]