# property:development:construction:services:electricity:solar #

<callout type="Navigation" class="small">

* [[../|(UP)]]
{{indexmenu>.#2|nsort tsort}}
* See:
  * https://www.princeton.edu/news/2022/06/29/once-seen-fleeting-new-solar-tech-proves-its-lasting-power
  * https://climatedrift.substack.com/p/why-solarpunk-is-already-happening


</callout>


<panel title="Summary">

</panel>



## Calculations ##

Assuming for a tiny home:

* Calculate *max* instant power load:
  * Note:
    * Average Tinyhome is 4000W.
  * 5 x 10W lights = 50W 
  * 1 x 250W fridge = 250W (an economy fridge can get down to 70W)
  * 1 x 2000W oven/microwave = 2000w
  * 1 x laptop = 100W
  * 2 x 200W chargers = 100W 
  * 2 x 10W chargers = 20W
  * = 2520 W
  * An average kiwi house will also have:
    * more lights: 6 x 10W = 60W(normal house)
    * ext lights: 4 x 20W = 80W (outer lights, etc.)
    * Dish washer: 1 x 1.6kW = 1.6kW
    * Washing machine: 1 x 1kW = 1kW
    * Dryer: 1 x 3kW = 3 kW 
    * Water heater: 1 x 1.5kW = 1.5kW 
    * Heating: 2 x 2kW = 4kW
* Calculate *daily* power needs:
  * Note the max load is not for one hour, nor every hour of a full day.
  * Note:
    * Average Kiwi Household is 20kwH.
    * Average US household is 30kwW.
    * Average is *NOT* the same as Max Daily (eg: winter).
    * We use 27hwH. Up to 40kWh.
  * The energy consumed is:
    * Lights: 50w x 6h = 300Wh
    * Oven/Kettle: 2000w x 1h/3 = 666Wh
    * Fridge: 250w x 24h/3 = 1000Wh
    * Laptop: 60w x 10h = 600Wh
    * Chargers: 100w x 4h = 400Wh
    * Chargers: 10W x 12h = 120Wh
    * = 3.1kWh, rounded up to 4kWh, which is pretty average.
    * Compared to an average house, which has in addition:
      * Lights: 60W x 6h = 360Wh
      * Outdoor lights: 80W x 3h = 240Wh
      * Dishwasher: 1.6hW x 2/3*1h = 1.2kWh
      * Washing machine: 1kW x 2/3*1h = 1kWh
      * Dryer: 3kWx 2/3*1h = 2kWh 
      * Heating: 4kW x 4h = 16kWh
      * Water heater: 4kW x 2.5h = 10kWh
      * So that's the base 4kW + 6.2kW = 8700kWh + 10000kWh => a whopping 27,0000kWh (The average for NZ is 20kWh. The average for US = 30kWh. But then there's winter, where it rises considerably due to heat needs). 
  * So, as a recap,  the daily load is:
    * after adding a 25% margin of omissions and future needs (electric car)
    * Tiny Home: 2553Wh * 1.25 = 3830kWh.
      * Bump it up to 4kW, and you have enough to run a dishwasher. Or washing machine. But not both. And no drier of course.
    * Average House: 20000Wh * 1.25 = 25000Wh
* Calculate solar panels array:
  * If not using a battery, one would be working with use max load...noting you'll only really be able to use it 3hours a day. Kinda useless.
  * But if using a battery, use the *daily* power needs as a starting point.
  * Need is equal to 'Total Daily Power Consumption (Wh) / Peak Sun Hours per Day = Solar Panel Wattage (W)'
  * Tiny home needs: 4kWh / 3h (max kiwi sun in summer) = 1200W needed from panels.
  * House needs: 25kWh / 3h  = 7250W needed from panels.
  * Which can be developed by eg: 5 x 200W, 7x150w, 4x300w, 4x320W or 3x350w would work. 3x310W is a bit light.
* Calculate battery bank needs:
  * Total Daily Power Consumption x Days of Autonomy / Battery Voltage = Battery Capacity (Ah)
  * 3125 Wh x 3d / 12V = 9375Wh / 12V = 781Ah
  * One could use: 
      * 4x200Ah battery...a whopping 4x$2129.Ouch.
  * Or cut down to 2d:
    * 3125 Wh x 2d / 12V = 6250Wh / 12V = 520Ah. Which is 3x200Ah batteries. Still Outch.
  * Or start with just one day backup (note more wear on batteries due to full discharges):
    * 3125 Wh x 1d / 12V = 3125Wh / 12V = 260Ah. Which is 2x200Ah battery 
      * While you technically can, don't change size in batteries (eg: 2x200Ah + 1x200Ah) as uneven dis/charging ages batteries fast.
* Calculate the solar charge controller:
  * used to control flow from solar panel to battery to not overcharge it.
  * important to choose one that is larger than both the source panels and closer to the target batteries current.
  * Read the panel's specsheet or calculate A from known V to determine maximum current all panels can generate:
    * Assuming 3x340w panels, at 34.73V, 
    * 340/34.73V = 9.79A per panel
    * So it's 3 panels x 9.79A => 29.37A Max current output.
  * Calculate the max current the battery can accept:
    * It is probably not the same as what the battery can produce. eg: Specs says max charge rate is 50A.
  * So, min 30A, better if one can afford 50A.
* Calculated the Dump load:
  * used to dissipate excess electricity generated by solar panels, as heat
* Calculate inverter: