A Solar Power System for a Residential Application. Written by Osman N. Muneer

Transcription

1 A Solar Power System for a Residential Application Written by Osman N. Muneer ECET 490 Final Report Due: 12/18/08 Instructor: Paul I-Hai Lin, P.E. (EE) Faculty Advisor: Iskandar Hack, P.E. (EE) 1

2 Table of Contents Introduction.3 Statement of the Problem...4 Market Analysis 4-5 Requirements...6 Specifications...7 Implementation Methods & Solutions. 8-9 Regulatory, Standards, Safety & Quality Issues 10 System Description with Block Diagram.10 Trade off Study 11 Required Resources 11 Gannt Chart.13 Estimated Project Cost...14 Predicted Return of Investment.14 Potential Benefits.15 Risk Analysis 15 Bibliography.16 2

3 Introduction A solar power system is a system which converts energy from the sun into usable electricity. It is used to heat our homes, pools and spas, and water we use. The solar power system is composed of four components. 1.) Solar panel 2.) Solar charge controller (regulator) 3.) Temperature sensor 4.) 12 V lead acid battery 5.) Inverter (AC to DC) I will evaluate, build, and test a solar charge controller for phase 2. The primary objective of a charge controller is to prevent the battery from overcharging and to block any reverse current. It does this by regulating the voltage and current coming out of the solar panel and going into the battery. A built-in circuit with a diode prevents any reverse current flow. 3

4 Fig. 1 [1] (Block diagram of solar system components) A block diagram of the solar system components is shown in [1]. This is to give an idea of how the system is laid out and get a better understanding of the flow of things. The 12 V solar panel absorbs the energy from the sun and converts it to usable DC electricity. This DC electricity than goes to the charge controller where it is regulated to a safe level before it goes to the battery and is use for powering the television. The DC electricity must be converted to AC electricity in by the inverter which is required for providing power to the television as well as to home appliances. However, light bulbs do not require an inverter and only operate on DC electricity. These are the components which make the solar power system a whole system. Statement of the Problem I want to make a solar power system where a device could be added so that the solar charge controller can receive a signal to stop getting voltage and current from the solar panel and stop sending voltage and current to the battery because it is fully charged. The device is a battery temperature sensor. 4

5 Market Analysis The Maximum Power Point Tracking solar charge controller is the most efficient in today s market and its specifications are shown in [2]. They are relatively new to the solar energy industry. These charge controllers are different than the traditional Pulse Width Modulator charge controllers in that they are more efficient and in many cases more feature rich. Maximum Power Point Tracking charge controllers allow your solar panels to operate at their optimum voltage, improving their performance by as much as 30%. Traditional Pulse Width Modulator charge controllers reduce the efficiency of one part of your system in order to make it work with another. Several Maximum Power Point Tracking charge controllers can accept high input voltages (up to 120+V DC) from your solar array and efficiently down convert the DC voltage to that of your system (e.g. 12, 24, 48VDC, etc) which means you aren't losing any generated power and you are able to use what you generate more efficiently. Additionally, using a much higher DC voltage on the input side allows you to use thinner wire, decreasing your wire cost and making installation easier. Fig. 2 [2] (Outback Power FLEXmax80 MPPT Solar Charge Controller) Maximum Power Point Tracking solar charge controller (MPPT) most efficient in today s market 5

6 more features more expensive than PWM (Pulse Width Modulator) MPPT is better investment for long haul Total cost is $ Fig. 2 [2] (Outback Power FLEXmax80 MPPT Solar Charge Controller) Requirements Before buying a solar power system, there are requirements that must be performed by the owner of the place of residence. Calculate your AC and DC loads o determine your weekly watt-hours per week o size of the panel depends on how much power is required by your appliances o must know how much energy your battery can store Inverter Selection o selection based upon your load calculation Solar Array Sizing o figure out average sun hours per day in your area o go to Solar Energy Maps page or check local whether data Battery Size o 12 V cannot be carried efficiently through long cable to battery 6

7 o If distance between panel and 12 V battery is greater than 75 feet, than use 24 V battery Specifications Table 1 shows the solar panel system components in the left column and the requirements satisfied by them in the right column. Solar Panel System Solar Panel Solar Charge Controller Battery Temperature Sensor 12 V Lead Acid Battery DC to AC Inverter Requirements satisfied by solar power system components Absorbs energy and converts it to usable power. Protects battery from overcharging and is a voltage and current regulator. Sends signal to charge controller indicating battery temperature. Provides power to the load and stores excess energy. AC is required for home appliances and television. Table 1: Component specifications 7

8 Implementation Shunt transistor Fig. 3 [3] (Circuitry of solar charge controller) 8

9 In [3] the circuitry of a solar charge controller is shown. The principle and explanation of a solar charge controller is simple. There is a circuit to measure the battery voltage, which operates a switch to divert power away from the battery when it is fully charged. The shunt transistor disconnects the solar panel when a certain voltage is reached. It also disconnects the load if the battery voltage is too low. Both switches are never open at the same time. Methods and Solutions Solar Panel o Calculate how much energy it can generate over a period of time. 1) Multiply the panel wattage by the number of hours exposed to sunshine. 2) Multiply the result by 0.85 (factors allow for natural system losses). Example: For the 50 W solar panel in 4 hours of sunshine, 50 X 4 X 0.85 = 170 Wh is generated in 1 hour This is the amount of energy that the solar panel can supply to the battery. 12 V lead acid battery o calculate how much energy you can store in battery. o convert battery amp-hours into watt-hours by multiplying amp-hours by the battery voltage. Example: For a 50Ah, 12 V battery this is: 50 X 12 = 600 Wh This means the battery could supply a 60 W light for 10 hours. 9

10 Load use over a period of time o calculate how much energy our appliances use over a period of time. o Multiply the power consumption by the hours of use. Example: A 13 W fluorescent is on for 5 hours, so it will take 13 X 5 = 65 Wh Regulatory, Standards, Safety & Quality Issues The Underwriters Laboratories is approved by the American National Standard Institute and provides safety standards for V batteries and DC to AC inverters. The UL Standard /Subject #458, section 1.5 covers this. System Description with Block Diagram 10

11 Battery temperature sensor Fig. 4 [4] (Block diagram of solar power system) In [4] a block diagram of a solar power system is shown. The 12 V sends the DC output to the solar charge controller where it is regulated. A battery temperature sensor is connected to the terminals of the battery and sends a signal to the charge controller of the batteries temperature. This prompts the charge controller to adjust its settings in provide a appropriate charging as well as to protect the battery. Trade-off Study Solar power system vs. engine-generator (gas powered) Solar power system has more advantages than an engine-generator. o no fuel o no emissions o clean energy o low maintenance o easy to install o low recurrent costs Engine-generators provide electricity for places that have no power grids. o can be reliable when solar power cannot meet our electric needs o winter storms, windless day, battery charging 11

12 o Noisy, dirt, fumes, not emission-free, high fuel costs Required Resources Estimated cost of a solar power system is $10k to $100k. Requirements o where are you in the world o how much sun do you get per day o record power rating of all your appliances to find out how much power you require o residential installation times range from 3 days to 4 weeks, depending on the system size. 12

13 Gantt Chart 13

14 Estimated Project Cost Table 2 shows each component required to build a solar panel system and the breakdown of the cost for each. The total cost of the solar power system is $2, Table 2: Total cost of components Predicted Return on Investment When investing in a solar power system, you obviously want to gain something back. The extra kilo-watt hours of electricity stored in your battery can be sold to the local electric utility company for a fee. You can also save $1,000 to $2,000 per year on your electric bills. Return of Investment = ($5000 $2,935.50)/$2, = Local utility company pays you for any excess power that the battery produces. 14

15 Save between $1,000 to $2,000 per year on your electricity bills. Potential benefits Learn how to integrate your own residential solar power system. Gain knowledge of all components in a solar power system and know what their primary function is. Develop the skill of connecting components with wires and cables. Provides good experience in a potential career. Risk Analysis Table 3: Risk Analysis 1) Not having sufficient knowledge to complete the solar power system. 2) Installing the solar power system incorrectly. 3) Being too hasty in your decision making and not buying the proper equipment. 4) Not knowing the proper safety conditions when working with the equipment. 15

16 Bibliography [1] The Infinite Power of Texas ( Introduction to Photovoltaic Systems. [2] [3] [4] [5] 16