The details of our panels:
- 10 x Hyundai HiE-S410VG (10 x 410Wp)
- 10 x Enphase IQ 7A microinverter (IQ7A-72-2-INT) 366 w
- a battery could be installed into the system at a later date but currently we have no electricity storage in the house
- Installation cost 7916.13€ (Sept 22) by Green Electric (who I would highly recommend)
A couple of points to note on our electricity supply:
- It took a couple of months after the panels were installed (until end 2022) to switch to the solar tariff offered by Endesa (Spanish electricity supplier)
- The details of the tariff we are on (Solar Simply) are:
- Cost of electricity : 0.149072 €/kWh (+ 5% IVA)
- Price for energy exported : 0.1 €/kWh
- We are only compensated up to the amount of electricity used so we never get 'paid' only 'free' electricity (if we export approx 1.5 times the amount we use)
- Between Mar-Oct the panels produce sufficient electricity such that we have not had to pay for any actual electricity (although we do pay for the hire of the supply and the meter and other stuff) so our bills come in around ~25€/month
Comments:
- The solar panels produced the most energy (25.6kWh) on 7/8/23. Each individual panel produced between 2.63kWh and 2.39kWh (this panel is often slightly shaded by a communications tower on an adjacent roof).
- We had no data on our actual electricity usage in the house prior to moving in. Actual usage so far in 2023 is 2,900kWh (though the house has been mostly unoccupied since mid August 2023)
- When unoccupied the fridge, router, security camera, (holiday mode) heat pump etc use ~1.9kWh / day or 55kWh / month (which would cost us about 8.19€ a month)
- Until June 2023, water was heated by two electric water heaters (one very old 15l one for showers, one newer 80l for downstairs) (on smart plugs set to be 'on' during the height of the day to use solar energy as far as possible)
- The kitchen was installed in April 2023 - before this we cooked with a two ring portable induction hob, microwave/oven combi and InstantPot. We had no oven or dishwasher.
- This graph shows our daily energy consumption by hour (from a typical day in May 2023) (note the peaks when the kettle was boiled for the morning coffee, and when dinner was prepared in the evening. Other use through the day includes washing machine and water heating with smart plugs turning on the immersion heaters)
- Until Oct 2023 any heating of the house was done by wood burning stove (living room only) or three oil filled electric radiators (on smart plugs)
- As of Oct 2023, we have a heat pump for DHW and underfloor heating in the main (55m2) vaulted room but other heating for winter 23/24 will be oil radiators and wood burning stove until we can get the fan coils installed for heating/cooling.
- Our electricity tariff pre 'Simply Solar' incentivised use of electricity off-peak (between 12am and 7am) so the washing machine was often run overnight. With the solar energy the washing machine (and as of June 2023, dishwasher) is run at the height of the day to use solar energy (where available).
Calculations
- Based on annual consumption of 8,200kWh it was estimated we would pay back the panels in 6 years.
- To calculate the maximum energy the following data was used by Green Electric
- The latitude/longitude of the panels : 41.91746636, 3.165087223
- average daily/monthly solar irradiance (GHI, from the lat/long and GlobalSolarAtlas) : 4.682 kWh/m2/day or 4.682 peak sun hours (averaged throughout the year); the data used by Green Electric has monthly irradiation figures, which seems a much better idea than annual!
- Simply, the panels should product (10 x 410W) 4.1kW/h with full solar radiation. Multiplying that with the monthly global radiation (sometimes known as hours of full solar radiation) and summing it all gives the values below.
- As stated in our Green Electric quote, 'These calculations already include all the loss of performance of all the elements that make up the installation' - I've read in a couple of other places that a factor of 1.2 is used to cover 'system inefficiencies'.
- At 0.149072€/kWh, this energy would have cost 812.19€ giving a break-even point around 10 years (not 6 - Green Electric used a 0.22€/kWh unit cost)
- In the 'pay back time' estimate, there was no surplus energy produced by the panels that was not used in the house. This has not been the case in this first year (and probably won't be the case in subsequent years as the house will not be permanently occupied for a while at least) Also, it's not possible to only use energy when there is solar energy - some of our energy is used when there is no sun. As mentioned above, the 0.1€/kWh compensation we receive from Endesa for energy given back to the grid covers this amount from March - October.
- The below table shows that we have consumed less than a quarter of the energy our panels have generated 2023 so far. This gives a total saving of 234.6€ for the solar energy we have used, and 116.35€ for the energy we have given to the grid.
- As important as the money savings, possibly more important is the amount of CO2 that wasn't produced by the electricity grid because panels produced the electricity renewably. The kg of CO2 not produced is calculated assuming all the solar energy we produced was used by the grid - KwH multiplied by a factor (the CO2 emission intensity) determined by country by The European Environment Agency. The value for Spain (from 2016) is 0.265.
- Green Electric estimated the 25 year saving would be 54 tonnes (compared to the 33.7 tonnes my estimate gives). I suspect they used a different CO2 emission intensity factor (2016 is quite a long time ago; worryingly though the 0.238 factor their calculation uses means that Spain's CO2 emissions / kWh produced by the grid have increased, not decreased as I would have expected)
- UK calculations would likely use data from Department for Business, Energy and Industrial Strategy where the conversion factor for 2023 is given as 0.20707 kg CO2 saved for each kWh produced from a carbon free source.
- We can, and will, be using much more of our solar energy when we're at the house in 2024. The efficiency of the heat pump to heat the underfloor of the main vaulted room is yet to be tested, and we will be installing fancoils in the bedrooms for cooling/heating.
- We also hope to install a swimming pool at some point maybe...
- Green Electric's estimates were mostly accurate, albeit they had no information on our energy use to work from.
- Possibly we could have installed a few less panels - but let's see what the winter brings...
- It currently doesn't seem that there would be much value in a battery in the system as we are producing enough excess energy to compensate for the cost of the electricity we import. This might change once we start to use heating/cooling when there is no solar energy (when the sun's down)
No comments:
Post a Comment