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electrical:solar [2017/05/28 12:34] frater_secessus [Solar power] |
electrical:solar [2020/10/11 19:48] 127.0.0.1 external edit |
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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 paying for it!) is [[electrical: | + | The most difficult part of a solar power system (other than [[electrical: |
- | ===== sizing a solar installation ===== | + | |
- | ==== amp-hours needed ==== | ||
- | 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 | + | ===== do you really |
- | If you are going to be using both 12vdc and 110vac (through an inverter) it may be easier to do the calculation in watts, then convert to Amps DC by dividing by 12. Otherwise an [[https:// | + | Maybe not. If any of these conditions are met you probably don't need solar: |
- | Note: | + | * you stay in campgrounds or other places with access to [[electrical:shore_power|shore power]] |
+ | * you have a [[electrical: | ||
- | === 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. | ||
+ | |||
+ | There are times (bulk, early absorption) when the system is struggling to charge the lead-chemistry bank; loads should be minimized during these periods. | ||
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+ | At other times like late absorption and float the system will have [[electrical: | ||
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+ | ===== 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: |