Solar Thermal. The sun is but a morning star. Henry David Thoreau

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1 Solar Thermal

2 Solar Thermal The sun is but a morning star. Henry David Thoreau

3 Introduction Solar Thermal History The Basics Solar Collector Basics

4 Solar Thermal History 1200s - Anasazi people built south-facing cliff dwellings for passive solar design Horace de Saussure builds first solar collector First solar water heater patented 1900s - Rise in popularity (particularly in sunny areas)

5 Solar Thermal History Passive solar homes in huge demand in post-war America 1950s - World s first solar-heated office building Late 1970s - Oil embargoes, rise in renewable energy 1980s - Rise of cheap oil, decline of solar 2000 s Decline of cheap oil, rise in solar

6 The Basics Solar Hot Water (SHW) can be used for heating Domestic Hot Water (DHW) and/or for space heat (Combi) SHW is more forgiving than PV o Tilt, orientation, and shade aren t as critical

7 The Basics: Components Collectors Tanks Pumps Controllers Plumbing o o o o Flow meters Temperature and pressure gauges Air eliminators Valves

8 Difference Between Solar Thermal and PV Solar thermal circulates fluid through the outside unit Solar PV generates electricity from solar cells in the panel

9 Solar Collector Basics Solar radiation hits the collector and is absorbed as heat This heat is transferred from the absorber to a heat transfer medium (Aluminum, oil) This heat is then transferred to the water or Heat Transfer Fluid (HTF)

10 Parts and Pieces of a Solar Thermal System

11 Siting Orientation Tilt Shade Roof construction

12 Siting: Orientation South (180º) provides for the optimal sun collection Loss of ~25% efficiency by orienting the collectors either East (90º) or West (270º)

13 Siting: Tilt Solar DHW otilt = latitude (at least 40º for snow shedding) Solar space heating otilt = latitude + 15º

14 Siting: Bull s Eye Chart Third, determine % irradiation where arc and line cross This location provides 95% solar irradiation Second, determine orientation angle (eg 10º West of South 190), draw line First, determine mounting angle, draw arc

15 Siting: Bull s Eye Chart Mounting at 50 degrees and facing due East This location provides 80% solar irradiation. This shows the tolerance solar thermal has over PV

16 Siting: Shade Not as critical for solar thermal collectors as is for PV Rule of thumb: If 10% of the collector is shaded at any time, it is 90% efficient

17 Tools and Resources Solar Pathfinder ohttp:// Solmetric ohttp://

18 Example Measurement - Solmetric It is just as necessary to determine your solar insolation for solar thermal as it is for solar PV.

19 Siting: Roof Construction Age of roof Type of roofing Structural integrity o Will trusses/rafters support extra weight? Method of getting materials to the roof

20 Considerations Needs Assessment Components Design Types DHW systems Combi systems Classifications Tools Rating Systems

21 Needs Assessment Points of Interest: Has the household taken measures to reduce heating/dhw use? o o Energy audit Low-flow faucets/shower heads, etc. Determine DHW usage o o Utility bill analysis Number of showers a day & length, etc. Determine solar fraction (amount to be replaced by solar hot water) household desires o 50% (minimum for incentives) 100%

22 Components 1. Solar collector 2. Expansion tank 3. Pump station 4. Solar storage tank 5. Control system 6. Heat source

23 Components: Solar Collector Types Unglazed Glazed (Flat Plate) Evacuated Tube Concentrating (Trough)

24 Collectors: Unglazed Provides heat less than 110 F Does not have glass or other transparent covering Commonly used for swimming pool heating systems

Collectors: Glazed (Flat Plate) Panels provide

25 Collectors: Glazed (Flat Plate) Panels provide heat around F Often used for DHW and space heating Cover of glass or other transparent material Most common type of collector

26 Collectors: Glazed (Air-type) Sun heats air rather than water in the collector Most commonly used for space heating applications Typically mounted vertically on wall of building

Collectors: Evacuated Tubes Tubes provide heat around

through a heat exchanger Solar collecting fin is inside a

the environment Used for space heat and DHW DOUBLE-WALL

27 Collectors: Evacuated Tubes Tubes provide heat around F Liquid rises to top of tube to heat pumped water through a heat exchanger Solar collecting fin is inside a vacuum tube to prevent solar from reradiating back into the environment Used for space heat and DHW DOUBLE-WALL INSULATION TUBE

water and run a turbine http://blog.hasslberger.

28 Collectors: Parabolic (Trough) Provide heat above 180 F Used by utilities and power-producers Used to steam water and run a turbine rmal_pow.html

29 Comparison of Different Collectors As the difference between the fluid in the collector and the outdoor air temperature increases the efficiencies drop. Evacuated tube collectors work better at providing higher temperature water.

30 Flat Plate vs. Evacuated Tube

31 Comparison Continued Flat Plate Efficient in temperate climates Easy to attach to roofs Less-expensive option Long track record Can shed snow Evacuated Tube More efficient in cold climates Produces higher temperature water Possible to replace one tube out of an array in case of failure Glass requires handling care Requires more roof space than flat plates Cannot shed snow easily

Components: Expansion Tank Stagnation is when sunlight is incident to the collector, but no fluid moves through it to remove the captured energy (heat).

32 Components: Expansion Tank Stagnation is when sunlight is incident to the collector, but no fluid moves through it to remove the captured energy (heat). In the event of stagnation: o Collectors may reach 350 F during peak sun o The collector fluid changes to a vapor. o This added vapor and hot liquid volume is displaced to the expansion tank. Sizing of the tank depends on: o The number of collectors o Local codes Pages/Expansion-Tank.jpg

33 Components: Controllers Set-point activates or deactivates an output device when the temperature reaches a certain level Analog Differential Monitors a change in temperature between two points Digital Differential More variety of functions available to user than analog controller

34 Components: Pumps Types of pumps: Single speed drive Multiple speed drive high, medium, low Variable speed drive Changes based on the demand of the system ail/kategorie/1/id/3/sprache/en-us

Components: Pump stations Solar circulation stations are

Sizing and desired control features need to be assessed

35 Components: Pump stations Solar circulation stations are available that combine pumping and control devices. Sizing and desired control features need to be assessed before purchasing a pump station ce.com/solarthermal-hotwater/solar-thermalhot-water.html axxsolar.com/so lar-hot-waterpumpstations.php

Components: Storage Tanks Types: Pressurized o Heavy o Expensive Unpressurized o Longer life o Larger o Less maintenance Selecting the right size: Flat

36 Components: Storage Tanks Types: Pressurized o Heavy o Expensive Unpressurized o Longer life o Larger o Less maintenance Selecting the right size: Flat Plate 1Gal/sq. ft of collector area Evacuated Tube 1.5Gal/sq. ft of collector area

37 Components: Plumbing Copper piping Temp. & pres. gauges Flow meters Air eliminators External heat exchanger Mixing or anti-scald valves Check valve Shut off valves Drain/fill valves Pressure relief valve

38 Design: Principles The cooler the collector array operates the lower the thermal losses and the higher the efficiency Conventional energy sources should only be used when needed to supplement the solar energy The collector and all piping must be protected against freezing

39 Solar DHW

40 Design: Solar DHW Determine DHW usage o From energy bills o Residential - assume gal. Per person per day Estimate flat plate collector area o 20 Sq feet of collector area for each of first two household members o 12-14SF for each additional member for northeast Storage volume o Typically 1 gal 2 gal per square foot of collector area.

41 Combi Systems

42 Design: Combination Solar Systems Most residential combi-systems treat DHW as the primary load to take advantage of the high solar availability in summer Typically use greater collector area and larger storage tanks relative to DHW systems It is important that combi-systems have a method of dealing with excess heat production in warm weather Only efficient with low temp heating like radiant floor

43 Design: Classifications of Systems Active Fluid is pumped through the system Passive Thermo-siphoning is used to move fluid through system (convective currents) Open-loop (Direct) DHW or pool water is pumped through collector Closed-Loop (Indirect) Heat is exchanged between the collector fluid and the DHW

44 Design: Types Closed-Loop Pressurized (Active, Indirect) Drainback (Active, Indirect) 09/02/01/Solar-Loop-Pressurization

45 Design: Types Thermo-Siphoning (Passive, Indirect) Draindown / Pool System (Active, Direct) Works.asp 09/02/01/Solar-Loop-Pressurization

46 Closed-Loop Pressurized System Requires: Antifreeze A pump (or two if space heating) Separation from potable water Expansion tank Heat dump

47 Closed-Loop Pressurized System Advantages Piping between the collector and storage tank may be installed in any orientation Circulator pump can be very small, and may possibly be operated by small DC motor powered by PV Disadvantages Collectors must operate at higher temperature. Glycol solution is subject to breakdown and requires periodic maintenance (every 3 years) Stagnation caused by o Sensor failure o Full hot water tank o Power outage

48 Drainback Systems Drains every time the pump is not circulating fluid through the array Each time the pump restarts, warm tank water enters the tubes Prevents freezing without glycol Decreases standing heat loss in array when demand is low Array must be sloped and tilted so water drains to bottom corner exit

49 Thermo-Siphoning System Storage tank must be above the collectors Water is heated through convective currents within the collectors

50 Draindown Pool Heating System Water is drained out of system during non-use periods Pool water is run directly through the collectors

51 Tools Publications, other software RET Screen Simulation software to study the technical and economic feasibility of active solar energy systems Free download from F-Chart Method for predicting solar performance and economic viability Used in the solar industry for over three decades Available from:

52 Rating Systems Solar Rating and Certification Corporation (SRCC) Independent third-party certification organization Administers national certification and rating programs for solar energy equipment Collector certification (OG-100) Any part of a solar energy system that is exposed to the sun and collects the sun s heat Heating system certification (OG-300) Certification program for solar hot water systems

53 Rating Systems SRCC determines whether systems meet minimum standards for system durability, reliability, safety and operation Factors affecting total system design, installation, maintenance and service are also evaluated.

54 Costing Component Costs Incentives Examples

55 Components Component Cost Units Notes Collectors $40 Per SQFT Storage Tank $10-15 Per Gal. Controls $1,400 Per Unit Racking $600 Per Panel Averaged costs from an actual install Plumbing $1,200 Per Panel Labor $550 Per Panel

56 Current Solar Thermal Incentives Grant Programs NYSERDA Solar Thermal Incentive Program (PON)2149 Federal Tax Credit Program Personal tax credit Energy Conservation Improvements Tax Credit $1.50/kWh displaced annually up to a maximum of $4,000 per site/meter Systems must generally supplement and existing electric water heater Deduct 30% of the after incentive cost of the Solar Thermal system with no upper limit, 50% solar fraction required Credit of 100% of the added value to the property Visit for the current incentives offered from state and federal governments

57 Current Solar Thermal Incentives NYS Tax Credit Program Residential Personal tax credit Deduct 25% of the after incentive cost of the Solar Thermal system up to a maximum of $5,000 Excess credit may be carried forward five years Sales tax exemption 100% exemption from state sales tax

58 Solar DHW Design Exercise 4 person household, Ithaca NY:

59 Solar DHW Design Exercise 4 person household, Ithaca NY: (20 SF * 2 people) + (12SF * 2 people) = 64SF Select (2) 4'X8' flat plate solar collectors; area = 64SF Storage tank sized 1 gal to 2 gal/sf of collector area = 64SF * 1 gal/sf = 64 gal. Select 80 gal storage tank

60 Costing System Cost (3 Panel, No. of Collectors (AET) 3 Cost of Collectors $3,150 Closed-loop Pressurized) Racking $2,000 Storage Tank $1,350 Plumbing & Controls $2,800 Labor $1,600 Total (pre-incentives) $10,900 NYSERDA Rebate ($1.50/kWh, $5k cap) $5,000 Cost after Rebate $5,900 Fed Tax Credit (30%) $1,770 State Tax Credit (25%) $1,475 Final Cost $2,655

61 4 common questions FAQ s

62 Q: Question Does solar thermal #1 work in cooler climates? A: Solar thermal systems still produce hot water during cold weather. They produce more hot water in the summer time and in warmer climates, but they are an effective technology in cool areas, too.

63 Question #2 Q: How much space does a solar thermal system require? A: Solar thermal systems require a water tank, much like a traditional hot water system. The bulk of the system, the tubes, are up on your roof and completely out of the way.

64 Question #3 Q: Does a solar thermal array only give you hot water during the daytime? A: Solar thermal systems have a storage tank, which keeps the hot water ready for whenever it is needed, even if the system is not producing a lot of hot water at the time.

65 Q: Will a solar thermal Question #4 system provide enough hot water for my whole family? A: Solar thermal capacity is related to how big of a system you install. Even if a small system is not providing enough hot water for a full house it can still provide valuable preheated water, which decreases the DHW load.

66 Take Away Points Summary : Siting Determining the site s receptivity for Solar Thermal o Minimize shading Shoot for less than 10% shading from 9AM 4PM o Optimize tilt Latitude + 15 for a Combi system, Latitude for DHW only o Optimize orientation Solar south gives the greatest hot water production

67 Take Away Points Summary : Siting Roof construction o Ensure roof has good structural integrity o Replacement of roof isn t within the next 5 years

68 Take Away Points Summary : Considerations Considerations: Tailoring the system to the customer s energy and budget requirements o Determine needs DHW only or DHW and space heat? o Determine load How much DHW used during the course of a year

69 Take Away Points Summary : Considerations Determine complexity of system o Drainback requires more engineering (less maintenance) o Pressurized is off the shelf in most cases (more maintenance)

70 Take Away Points Summary : Costing Determine the customer s budget o DHW can usually be met under $10k (gross) o Combi system can get really costly if trying to meet the customer s whole load Incentives: o 30% Federal tax credit o 25% State tax credit (NYS) o $1.50/kWh saved from NYSERDA

71 Take Away Points Summary : Costing No hike in property tax for 15 years (NYS) No sales tax (NYS) No capital gains tax

72 Resources: Planning and Installing Solar Thermal Systems Solar Engineering of Thermal Processes, 3 rd Edition Solar Heating Systems of Houses Solar Hot Water Fundamentals, Peter Skinner, P.E.

73 The End Questions?

74 Presenter Yossi Bronsnick ext. 118 Fax: Taitem Engineering, PC 110 South Albany Street Ithaca, NY

Solar Thermal. [Strategy]

Solar Thermal. [Strategy] [Strategy] Brief Description Solar domestic water heating (DWH) systems harvest the insolation from the sun and store its heat energy in the form of hot water. There are a number of factors that influence