5184608
Description
Flashcards by Shea Poage, updated more than 1 year ago
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Created by Shea Poage
over 8 years ago
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| Question | Answer |
| Solar radiation | Radiant energy emitted by the sun |
| Solar irradiance | Solar radiation that has reached Earth's surface. Power per unit area produced by the Sun. W/m^2 Measure of how much solar power you are getting at your location. |
| Solar irradiation | Solar irradiance integrated over time. Wh/m^2 |
| Solar insolation | The amount of solar irradiation per day Wh/m^2/day |
| Solar constant | The long-term average of the total solar irradiance. Quantifies the amount of radiation energy that arrives from the sun at the outermost layers of the atmosphere. 1.353 kW/m^2 |
| Air mass | The path length which light takes through the atmosphere normalized to the shortest possible path length (when the sun is directly overhead). AM=1/cos(angle from the vertical). When sun is overhead, air mass=1. |
| Ecliptic plane | Plane in which the Earth orbits the Sun |
| Equatorial plane | Plane containing Earth's equator and extending outward into space |
| Pyranometer | Measures global radiation in an area. Measures both direct and diffuse (reflected) radiation |
| Solar declination | An angle between the equatorial plane and rays of the sun |
| Solstice | When the sun will raise to either the highest or lowest path possible |
| Equinox | The sun will move across the sky for the same amount of time everywhere in the world |
| Solar time | Corresponds with the sun's position in the sky. Noon solar time is when the sun is highest in the sky |
| Solar altitude angle | The vertical angle between the sun and the horizon |
| Solar azimuth angle | The horizontal angle between a reference direction (typically due south) and the sun |
| Solar window | The area between the path of the sun at summer solstice and the path of the sun at winter solstice. |
| Array tilt angle | The vertical angle between horizontal and the array surface |
| Array azimuth angle | The horizontal angle between a reference direction and the direction an array surface faces |
| Solar incidence angle | The angle between the sun's rays and a line perpendicular to the array surface |
| Energy equation | Energy=power x time |
| V= | volts, V=IR |
| I= | amps, current, amperes |
| R= | resistance, ohms |
| W= | watts, power W=VI |
| Isc= | short circuit current. When you have all current and no voltage (wires are crossed/shorted) |
| Voc= | Voltage Open Circuit. When you have all voltage and no current (wires not touching/open circuit) |
| Imp= | Current Maximum Power |
| Vmp= | Voltage Maximum Power |
| Imp x Vmp = | STC watts |
| STC | Standard Test Conditions. Irradiance at STC=1,000 watts/m^2. Temp is 25C. 1.5 atmosphere spectrum of light. Does not take heat from irradiance into account. |
| MPPT | M |
| Wiring in series increases ________, wiring strings in parallel increases ________. | voltage, current |
| 120% rule | Busbar * 1.2 must be greater than or equal to the main breaker + backfeed (solar) breaker |
| Max current on PV source circuit= | Isc * 1.25, because sometimes we can get 1,250 watts per m^2 of irradiance |
| DC PV conductor sizing | Compare Isc * 1.56 and Isc * 1.25 and conditions of use, then pick the biggest conductor of the two. |
| What kind of wire is white? | Grounded current carrying conductor, usually negative. |
| What kind of wire is green or bare? | Grounding and non-current carrying for grounding equipment for safety |
| What kind of wire is black? | Hot ungrounded current carrying conductor |
| Wire sizes | Bigger wires have smaller numbers. Small wire=AWG 16, large=000 |
| Temperature correction factors for cold temperatures | Two ways: -PV mfg (?) gives temp coefficient of Voc (ex: 0.33%/deg. C). Multiply by delta deg C from 25 C for increase Voc in cold temp -If no coefficient from mfg, use table 690.7 (?) and multiply Voc by temp factor (If record low temp =-40C, correction factor is 1.25. If 40 Voc module @ 0C, 40V*1.25=50 Voc |
| Calculate circuit breaker size. | Inverter output max current * 1.25=circuit breaker size (round up) |
| Calculate battery sizing given days of autonomy and depth of discharge. | If you use 10 kWh/day, 3 days of autonomy, 50% depth of discharge: 10 kWh * 3 days = 30 kWh 30 kWh / .5 depth of discharge = 60 kWh in battery bank Then derate for other things |
| Peak sun | jk |
| Peak sun hours | jk |
| Consequences of array shading and best practices for minimizing shading and preserving output | Minimizing shading: take 3 times height of modules b/t modules Distance between rows= height * cos(azimuth)/tan(altitude) |
| Spacing distances | jk |
| Five key electrical output parameters | Voc: open circuit voltage Isc: short circuit current Vmp: max power voltage Imp: max power current Pmp: max power point Label on an I-V curve (current-voltage): Isc is high A, no V, Voc is high V, no A, and Imp and Vmp meet at the maximum power point. |
| Performance rating and measurement conditions | STC: 25 C, 1,000 w/m^2 SOC: 1,000 w/m^2 & nom (NOCT) temp NOCT: 800 w/m^2, 20 C, wind speed 1 m/s PTC |
| Overcurrent protection | jk |
| Conduit and raceway systems | jk |
| Switchgear | jk |
| Junction and combiner boxes | Combiner boxes: overcurrent protection for modules and conductors. Combines series strings in parallel. Need one per series string, and it needs a DC disconnect |
| Terminators | jk |
| Connectors | jk |
| De-rating factors and system losses | jk |
| Major components of a PV system | jk |
| A fall protection system must be in place for all work done at heights in excess of _______. | 6 feet |
| A circuit breaker performs the same function as ______. | a fuse, a switch, and over-current protection |
| What typically trips a breaker? | Not voltage...need more info |
| Between the main pane and the inverter, you have _______. | an AC disconnect |
| Between the array and the inverter, you have _______. | 2 of the following are correct: a DC disconnect, an AC disconnect, sometimes a charge controller |
| KNOW HOW TO READ A SUN DIAGRAM | ok |
| 2 phase is... | what is it |
| Utility interconnection is done in this order: | PV, charge controller, battery, inverter, grid |
| In California, magnetic North is pointing....? | More east than true north, BECAUSE...? |
| The critical design month is the worst case scenario where the load and the _______ are used to size the PV system | insolation data |
| If you combine solar and wind energy in an off-grid system, it is ______. | hybrid |
| Irradiance proportionally affects | amperage, NOT voltage |
| The further north you are, the better it is to | increase your tilt angle (match the latitude) |
| Temporarily shorting the output terminals of a PV module will | have no effect on the module |
| KNOW HOW TO READ A SUN PATH DIAGRAM | ok |
| When the sun sets on summer solstice, it is the farthest ______ that it will ever set. | north |
| The best way to increase your PV output is to | switch from stand alone to interactive (tracking?) |
| What factor inhibits higher voltages in PV? | hot weather |
| Linear current boosters | are commonly used in direct pumping applications and drop voltage |
| Irradiance is measured in | watts per square meter |
| The length of time a load is on... | is proportional to the energy used |
| Equinox | is the same day everywhere in the world at the same time |
| Ideal altitude and azimuth orientations for PV arrays | Year-round use: Summer only: Winter only: |
| What is the rule of thumb for estimating daily and yearly output for a PV array? | 1,000 kW per installed kW per year |
| Calculate the efficiency of a PV module. | Efficiency=Pmp/solar irradiance * area (m^2) |
| How to calculate appropriate distance between modules | Distance between modules = height of modules * cos(az angle between solar az and array az)/tan(sun altitude angle) |
| Why is DC current more dangerous that AC? | It is constant and more difficult to break |
| Ideal angle (altitude) of collector = | complimentary angle of sun chart's altitude |
| Charge controller | Purpose is to prevent overcharging battery, prevent reverse current flow, protect equipment from high voltage. |
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