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electrical:solar [2017/05/26 19:16] frater_secessus [Solar power] |
electrical:solar [2020/05/10 10:32] frater_secessus [mounting the panels] |
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+ | **Words of Wisdom:** I'm not sure people always grasp the concept of " | ||
+ | |||
====== Solar power ====== | ====== Solar power ====== | ||
- | Solar (photovoltaic or PV) power is an excellent fit for ' | + | [Note: |
+ | |||
+ | Solar (photovoltaic or PV) power is an excellent fit for ' | ||
Broadly speaking, **solar power systems consist of** [[electrical: | Broadly speaking, **solar power systems consist of** [[electrical: | ||
- | Under normal use solar setups charge during the daytime and discharge at night; the lowest [[electrical: | + | Under normal use solar setups charge |
+ | The most difficult part of a solar power system (other than [[electrical: | ||
- | ===== sizing a solar installation ===== | ||
- | ==== amp-hours needed | + | ===== do you really need solar? ===== |
- | There are calculators online that will tell you how much panel and battery you need. That is the easy part. | + | |
- | The **hardest part is figuring out what your daily power needs really | + | Maybe not. If any of these conditions |
- | If you are going to be using both 12vdc and 110vac (through an inverter) it may be easier to do the calculation | + | * you stay in campgrounds or other places with access |
+ | * you have a [[electrical:12v: | ||
- | Note: remember you can't use all the capacity of a battery; | ||
- | === number of days === | ||
- | |||
- | Build in capacity for days when there is little solar energy available: | ||
+ | ===== practical considerations ===== | ||
+ | * [[electrical: | ||
+ | * panels are coming down in price but are $$$ to ship. Where will you get them? | ||
+ | * wiring from the panels will have to enter the camper body somewhere, and the entry will have to be waterproof | ||
+ | * lead acid batteries (flooded, sealed, AGM, etc) are extremely heavy and bulky. | ||
+ | * wiring from power sources will need to be fused or fitted with circuit breakers | ||
+ | * how will you ensure your batteries don't run your batteries too low and damage them? | ||
+ | ===== scheduling your use of solar power ===== | ||
+ | //When// you use power from your system can be as important as //how much// power you use. | ||
- | ==== matching panels | + | There are times (bulk, early absorption) when the system is struggling |
- | A common rule of thumb is that there should | + | At other times like late absorption and float the system will have [[electrical: |
- | For a ~200AH 2x6v golf cart bank this would mean 200w-400w of nominal panel and a charge controller that can handle the panels' | ||
- | ^Scenario^Solar^Charge controller^Battery bank^Notes^ | ||
- | |minimal|200w|20A|2x6v 2p1s|Careful use of electric power. | ||
- | |ample|400w|40A|2x6v 2p1s|Pay attention to use of power but don't worry. | ||
- | |plenty|600w|45A-60A|4x6v 2p2s|Enough power that you usually don't have to think about it except in inclement weather. \\ Loads above, plus use of microwave, coffee maker, etc.| | ||
- | Make the most of the power provided by solar by [[electrical: | ||
+ | ===== things that affect solar power ===== | ||
+ | |||
+ | * Insolation (Intensity of sunlight) | ||
+ | * **strongest** when there is least atmosphere between the sun and panels: | ||
+ | * **weakest** when there is the most atmosphere between sun and panels: | ||
+ | * hours of sun each day - more in southern latitudes and in summer; fewer in northern latitudes and in winter | ||
+ | * clouds - panels make more power on sunny days and less on cloudy days, due to increased current (voltage relatively unchanged). | ||
+ | * temperature - panels make more power when cold, due to increased voltage (current relatively unchanged) | ||
+ | * physical obstruction / shade - as when in forested areas | ||
+ | * physical obstruction / covering - as when covered in dust or snow | ||
+ | |||
+ | |||
+ | |||
+ | ===== how much solar? ===== | ||
+ | |||
+ | Solar sizing has been moved to [[electrical: | ||
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===== weather-related issues ===== | ===== weather-related issues ===== | ||
+ | Weather and [[electrical: | ||
==== cloudy weather ==== | ==== cloudy weather ==== | ||
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* when the **sun is near the edge of a cloud** you can get spikes in current, called Edge of Cloud Effect (ECE). | * when the **sun is near the edge of a cloud** you can get spikes in current, called Edge of Cloud Effect (ECE). | ||
- | Rainy weather causes a drop in current due to the cloud cover effect. | + | Rainy weather causes a drop in current due to the cloud cover effect. An upside is it can wash dust off panels. |
Dusty or snowy weather can cause a loss of output due to physical presence on the panels. | Dusty or snowy weather can cause a loss of output due to physical presence on the panels. | ||
==== temperature ==== | ==== temperature ==== | ||
+ | |||
Panels yield the most power in cold temperatures. | Panels yield the most power in cold temperatures. | ||
+ | ===== mounting the panels ===== | ||
+ | |||
+ | [based on [[https:// | ||
+ | |||
+ | |||
+ | There are a few issues to consider: | ||
+ | |||
+ | * solar cells get very hot in sunlight, typically 25deg C hotter than ambient temps. Rating lab tests are performed when the cells are 25deg C (0deg C ambient, freezing) | ||
+ | * [[electrical: | ||
+ | hot panels re-radiate heat onto the roof of the van. "On my white van (even with a 5" airgap) it is hotter in the | ||
+ | shade under the panels than on the roof in direct sunlight." | ||
+ | * we prefer fewer holes in the van roof when possible | ||
+ | * " | ||
+ | * airgapped panels will add height for drive-through adventures | ||
+ | * taller racks will likely increase air drag and MPG, particularly if you drive fast | ||
+ | |||
+ | **Mounting hard panels to a rack** increases airflow (thereby reducing heat-related power losses), reduces heat transfer, and minimizes the number of holes in the van roof. | ||
+ | |||
+ | **Mounting hard panels directly to the roof** still allows some airgap (the depth of the frame) and the roof corrugations will allow some airflow in the direction of the " | ||
+ | |||
+ | **Mounting flex panels to the roof** allows some airflow in the corrugations but no airgap. Good news: panel derating won't be so bad because the heat is conducted to your van roof. Which is bad news if it's already hot in your van. | ||
+ | Opinion: |