ENERGY
We recommend discussing solar energy options in detail with local service providers, up to 2 or 3 different providers if possible. The following estimates generated from the WCL-Peru facility provide a helpful points of reference:
| UNIT | DESCRIPTION |
| 47 (± 10) kWh | → avg. 24hr consumption from an ISL Level 4 facility in active use (n = 43) |
| 70 kWh | → Maximum consumption |
| 30 kWh | → Minimum consumption |
| 40% | → laboratory load directly from PV system (24 hr) |
| 60% | → laboratory load from batteries (24hr) |
| ~34.2 kWh | → minimum battery capacity estimate = (47 x .6) + (10 x .6) |
| ~57 kWh | → minimum required energy production per day = 47 + 10 |
Table 1: The WCL-Los Amigos’s solar power requirements, as a reference
- OPEN maps.google.com → place a marker on your site location → right-click and copy the coordinates
- GO TO https://globalsolaratlas.info/map → paste the coordinates into the “SEARCH LOCATION” field. Select ENTER
- FIND “MAP DATA” → ensure you are selected on “SPECIFIC PHOTOVOLTAIC POWER OUPUT” → change units to “KWh/KWp per day” → record the value indicated (KWh/KWp)
- CREATE a table as shown below with the following column headings.
- Panel rating: the watts rating that is indicated on the panels you intend to purchase
- Panel number: number of individual panels that system could have
- Energy retention: this is the amount of energy that is available for work after electrical transfer and voltage conversion (80% retention is a reasonable estimate)
- kW production: calculated by multiplying the first hree columns and then dividing by 1000
- KWh/KWp: the value recorded from the Global Solar Atlas
- Peak production: calculated by multiplying the prior two columns together
| Panel rating (watts) | Panel number | Energy retention | kW production | KWh/KWp* | Peak Production |
| 270 | 60 | 0.8 | 12.96 | 3.93 | 50.93 |
| 270 | 70 | 0.8 | 15.12 | 3.93 | 59.42 |
| 270 | 80 | 0.8 | 17.28 | 3.93 | 67.91 |
| 270 | 90 | 0.8 | 19.44 | 3.93 | 76.40 |
| 270 | 100 | 0.8 | 21.6 | 3.93 | 84.89 |
IMPORTANT: PV POWER OUTPUT PER DAY is based on an annual average. In the real world seasonality results in lower or higher than the predicted output. In other words, more panels may be needed during dark, cloudy seasons to meet daily energy demands.
The basic calculation for calculating battery capacity is to multiple amp hours (Ah) by volts (V) by the total number of batteries and then divide by 1000 to obtain kWh. Accordingly, we can create a table as before.
| voltage (V) | Amp hours (Ah) | Battery number | kWh |
| 12 | 200 | 12 | 28.8 |
| 12 | 200 | 16 | 38.4 |
| 12 | 200 | 20 | 48 |
| 12 | 200 | 24 | 57.6 |
Consider a back-up generator large enough to simultaneously operate the laboratory and charge battery. The WCL-Peru has a 20 kW generator that is turned on for several hours at night if voltage falls below 48v before 19:30pm, or if a large amount of equipment will be running throughout the night.
Once a solar + battery system is installed it is important to monitor overall system health metrics to keep track of production and battery status.
Once a solar + battery system is installed it is important to monitor overall system health metrics to keep track of production and battery status. These include:
- total daily energy production (kWh),
- battery voltage,
- laboratory consumption (kWh).
Daily power “production to laboratory” compared to “production to batteries”.
Fig. 1. These data show the desirable trend, the solar system is large enough to run the lab and charge batteries during the day.
Daily battery charge – (minus) daily battery consumption = Daily battery remaining
Fig. 2. Daily battery charge minus daily battery consumption (WCL-Peru, n=90). Surplus (blue), deficit (red)
Overnight change in battery voltage
Fig. 3. Overnight change in battery voltage from 19:30 until the minimum voltage level that was recorded each morning, before solar energy production appears.