POWERMANAGEMENT
Is the solar energy glass half full?
David Freeman, Texas Instruments Fellow and engineering manager, Nagarajan Sridhar, Technologist at TI’s Solar Lab and Christopher Thornton,, Designer of Texas Instruments discuss the realities of solar energy.
T
he question of whether the glass is “half full” or “half empty” is often
answered based on whether you are optimistic or pessimistic. Solar energy critics generally come from the economics of solar energy installation. Once the installation is completed, the fuel cost is nearly zero. We will discuss the difference between considering $/W and $/W-h, and how module electronics can help optimize the system’s total energy. Bill Sweet [1] recently cited another Moore’s Law-like prediction: the cost of solar installation comes down about 20 percent for every doubling of installed capacity. Because this is not happening yet, the glass appears to be half empty.
The solar industry admits it needs help to reduce installation cost. However, they want the comparison based on $/kW h. The website Solarbuzz [2] tracks prices and trends. They draw a distinction between residential and industrial solar energy. Residential cost is about $0.35/kW h, whereas industrial is closer to $0.20/kW h. These numbers still indicate “the glass is not half full,” but getting close.
Rather than compare solar energy costs to other sources, shouldn’t the question be: “Do you want to live in a house powered by solar energy only?” This question was pondered by the Solar Decathlon. Each participant constructs a liveable house and is judged on everything from market appeal, day to day home activity, and engineering solution. Talking to the various student competitors, they think the glass is half full. They believe powering a house with solar energy makes more sense when energy efficient appliances are used.
Consider the desirability of a completely solar- powered house and corresponding efficient appliances, then indeed solar may be considered half full. Let’s look at the solar energy system and consider what can be done to improve performance.
Behaviour of PV modules
Solar cells, when connected together in series or parallel, comprise to form a photovoltaic (PV) module. In a typical residential or grid-tied application, the PV system has one or more PV modules connected in series to form a string to increase the overall system voltage. Each string is connected in parallel to form a PV array and increase the system current. The goal of this system or array is to deliver maximum power to the load. Since power delivered by a solar cell, module or array is the product of the current and voltage under DC conditions, it is critical to ensure that
19
www.solar-pv-management.com Issue III 2010
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56