PHOTOVOLTAIC (PV) SYSTEMS

Transcription

1 PHOTOVOLTAIC (PV) SYSTEMS picasaweb.google.com/jomo13/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 1 A PV system is a helio-electrical conversion process designed to produce electricity directly from solar radiation. A PV system would be classified as a transformer if installed as a building envelope element. A PV cell produces dc electricity; requiring an inverter [dc to ac] for most applications A PV system has cyclical output (corresponding to solar radiation intensity), thus requiring storage PV modules come in a variety of types (this is an evolving market) but efficiencies are rather low PV systems come in a variety of arrangements; with gridconnected the most common; the grid provides the storage Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 2 1

2 PV Module Types single (or mono) crystalline best-b2b.com/ polycrystalline amorphous renewablepowersolarenergy.com/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 3 PV Cell single crystalline PV cell: the original PV type; most efficient, most expensive; the cell is the basic building block of a monocrystalline PV system Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 4 2

3 Photovoltaic Cell Arrangement PV is an active system that harvests a renewable resource dc Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 5 Photovoltaic Cell Response typical PV harvests beyond the visible spectrum the spectral response varies with PV type pvpmc.org/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 6 3

4 PV Module modules using polycrystalline PV cells: newer, less efficient, less expensive Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 7 PV Module Opportunities flexible PV modules tinted PV cells/modules Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 8 4

5 PV Module Opportunities the Penn State 2009 Solar Decathlon house used cylindrical PV modules Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 9 PV Module Opportunities PV leafs transparent PV inhabitat.com/wp-content/blogs.dir/1/files/2010/05/solar-leaf-panels.jpg Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 10 5

6 Be Vigilant As a designer, you need to be both realistic and skeptical about products. Transparent PV is possible but this product does not change the laws of physics. Any photon that passes through the module is not available to produce electricity. Likewise, any photon that produces electric current is not available to assist with daylighting. transparent PV this fact does not mean this product is a bad design decision Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 11 Terminology: Cell > Module > Array cells are assembled into modules by the manufacturer; modules are sold as a product; arrays (involving multiple modules) are assembled on site to fit project needs Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 12 6

7 System Example: Stand-Alone dc PV System this approach involves no dc-ac conversion losses, but requires the use of dc appliances/loads (available, but not the norm for buildings) independent of the power grid; feeds DC loads; batteries required for storage Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 13 System Example: Stand-Alone ac PV System independent of the power grid; feeds AC loads; batteries required for storage; may include a backup generator Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 14 this approach involves dc-ac conversion losses, but allows the use of ac appliances/loads (ac is the norm for buildings) 7

8 System Example: Grid-Connected ac PV System connected to power grid; feeds AC loads; no on-site storage; perhaps net-metered; a very common approach this approach involves dc-ac conversion losses, but does not require on-site backup (batteries) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 15 PV Applications/Aesthetics various applications (retrofit and new construction): US Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 16 8

9 PV Applications/Aesthetics façade-mounted, roof-mounted, and guard-rail-mounted arrays: Europe Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 17 PV Applications/Aesthetics PV arrays used as shading devices; this is just so logical Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 18 9

10 PV Applications PV-powered car >> PV-powered pumping of solar hot water battery storage bank PV solar thermal Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 19 Example: PV Installation Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 20 10

11 Designed by McDonough + Associates involves a remodeling element (above ) and new element (next slide) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 21 Woods Hole Research Center (WHRC) Cape Cod, MA Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 22 11

12 WHRC PV main PV array ductwork for energy-recovery ventilator system the primary PV array covers all reasonably usable space on the new roof Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 23 WHRC PV secondary PV array (installed on remodeled portion of building) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 24 12

13 WHRC grid connection disconnect for utility company inverters to convert dc output to 208 V ac Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 25 WHRC also has solar thermal collectors note that the tilt angle for the PV panels is not the same as for the solar thermal panels: any ideas why? Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 26 13

14 Woods Hole Research Center PV 7 PM 6 February 2006 Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 27 Woods Hole Research Center PV 1:20 PM 8 February 2006 Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 28 14

15 UTA Solar Decathlon House Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 29 Lillis Business School U of Oregon an example of BIPV (building integrated photovolatics) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 30 15

16 Lillis Hall U of Oregon PV cells integrated with south-facing glazing Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 31 Lillis Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 32 16

17 Lillis Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 33 Lillis Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 34 17

18 Lillis PV cells integrated into south-facing skylights Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 35 BIPV: Building Integrated Photovoltaics This term describes the use of PV in such a way that the PV component either replaces another building component (such as a roof shingle or a shading device) or is integrated into such an element The fundamental idea behind BIPV applications is that building costs can be reduced by rethinking the PV module from an add-on device to a basic building enclosure component See Lillis Hall above for an example of BIPV Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 36 18

19 EXAMPLES: BIPV solarpowerpanels.ws/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 37 A VERY Useful PV Analysis Tool Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 38 19

20 Understanding PV System Size peak rating annual output Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 39 Summary Comments on Photovoltaics Basic technology is off-the-shelf (it is not experimental) Systems are also not experimental (dealt with by UL listings, electric companies, National Electrical Code) Technology and devices have gained respect (good track record) Most manufacturing is done off-shore (not in the US) Some use of small PV as distributed generating plants is being seen Typical PV efficiency is 15% (up to 20% at edges of technology) Efficiency is a constraint on design expectations (intent/criteria/cost) PV is an active system that uses a renewable resource (solar radiation) PV is an expensive technology Payback is beyond 15 years (perhaps 30 years) in a typical application System costs can be reduced by a grid tie-in and utility/tax rebates System costs should be reduced by BIPV (building integrated PV) There are some concerns about the environmental life-cycle cost/value of PV (considering manufacturing/disposal impacts on the environment), but the energy payback for PV manufacturing is estimated at about 4-5 years (embodied energy) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 40 20

21 PV Trends Efficiency sites.lafayette.edu/ efficiency trending upward, but with shallow slope Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 41 PV Trends Cost trending downward, with rather steep slope; but comparison with other electricity sources seems off-target (be careful with www data) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 42 21

22 PV Trends Contribution commons.wikimedia.org/ Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 43 Building-Scale Wind Power Small-scale (micro-scale building-installed or building-integrated) wind power systems are sometimes seen as an alternative to PV systems. The ability of small-scale wind devices to provide meaningful power to a building is elusive. horizontal axis turbines vertical axis turbines Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik

23 Building-Scale Wind Power Wind power potential: P = 0.5 x rho x A x Cp x V 3 x Ng x Nb where: P = power in watts rho = air density (about kg/m 3 at sea level) A = rotor swept area, exposed to the wind (m 2 ) Cp = coefficient of performance (0.59 {Betz limit} is the maximum theoretically possible, use 0.35 for a good design) V = wind speed in meters/sec (20 mph = 9 m/s) Ng = generator efficiency (50% for car alternator, 80% or possibly more for a permanent magnet generator or gridconnected induction generator) Nb = gearbox/bearings efficiency (depends, could be as high as 95% if good) there is no equivalent to PVWatts for wind system design analysis Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 45 Building-Scale Wind Power Example with 3-foot diameter blade: 3 ft (0.9 m) diameter blade, 6 mph (2.68 m/s) wind speed P = (0.5) (1.225) ((0.9/2) 2 x 3.14) (0.30) (2.68) 3 (0.75) (0.9) P = 1.6 W (1.6) (24) = 15 Wh/day 450 Wh/month Example with 6-foot diameter blade: 6 ft (1.8 m) diameter blade, 10 mph (4.47 m/s) wind speed P = (0.5) (1.225) ((1.8/2) 2 x 3.14) (0.30) (4.47) 3 (0.8) (0.9) P = 30 W (30) (24) = 720 Wh/day 21 kwh/month note the critical importance of blade diameter (affected by a square function) and of wind speed (affected by a cube function) on power production there is no equivalent to PVWatts for wind system design analysis Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 46 23

24 Why Site-Generated Electricity Matters electricity < > is a major component of total building energy load; getting to net-zero energy requires engaging electrical use Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 47 24