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Posted

Hi all,

I'm building a 450sqm house in Stellenbosch soon and have the opportunity to adopt proper renewable tech from scratch.  Your input would be invaluable.

So far I'm thinking double glazing, isoboard under slab,  PV and heat pumps.  Even considering geothermal (i.e. ground sourced energy input to heat pumps) 

Some more info:

My current consumption is ±70kWh per day in winter - conventional HWCs, cooking, pumps, minimal heating

The electric vehicle I'm considering will require an additional ±30-40kWh per day to cover my daily average travel.

I'd prefer an ROI of ±10-12% on the capital employed.

The system must be able to cope with stage 3-4 load shedding.

I never want to have to wear ski clothes in my home in winter.

I will have ±90sqm 30deg North facing roof surface (2 sections) and would prefer to use a panel that covers the whole of the roof section for aesthetical reasons.

My back of the cigarette box calculation - please rip it apart.

Peak winter 120kWh per day / 10hrs of sunlight = 12kW per hr generated

50kWh discharged during 14 non-sunlight hrs (charging elec vehicle and others) = ±50kWh battery capacity!!?

I look forward to engaging with the smart people here :)

 

 

Posted
1 hour ago, Sats Nkamoto said:

My current consumption is ±70kWh per day in winter - conventional HWCs, cooking, pumps, minimal heating

That's high. Well... depending on how many people are living on the property. But it is often the advice given on this forum that you need to reduce your consumption first, and then your solar dream gets easier to realise. So consider full gas stoves, keep an eye on geyser temperatures, put LED lighting throughout the new house.

I wouldn't trust myself to give good sums, but it might be a good idea to leave the final solar design until you know what your consumption is.

Here's some good tips on reducing electricity consumption
https://ltcelectricalservices.co.za/electrician-in-edenvale-and-bedfordview-boksburg-benoni-germiston-bruma-alberton/how-to-save-electricity/

Posted

It starts with the architecture that allows the house to use the winter sun to warm the walls(and keep the summer sun out), insulation that prevents heat loss(and ventilation to cool the house in summer). Then underfloor heating, geothermal heat pumps are better in places where the air reaches below zero celcius, the normal ones are fine for south africa.

50kwh storage is only 10-12 pylontech up5000 or BYD like in this system 

I would go with a similar system when starting from scratch and budget allowed.

Posted
6 minutes ago, Bobster said:

That's high. Well... depending on how many people are living on the property. But it is often the advice given on this forum that you need to reduce your consumption first, and then your solar dream gets easier to realise. So consider full gas stoves, keep an eye on geyser temperatures, put LED lighting throughout the new house.

I wouldn't trust myself to give good sums, but it might be a good idea to leave the final solar design until you know what your consumption is.

Here's some good tips on reducing electricity consumption
https://ltcelectricalservices.co.za/electrician-in-edenvale-and-bedfordview-boksburg-benoni-germiston-bruma-alberton/how-to-save-electricity/

Thanks, Bobster - I'll have a read

Posted
5 minutes ago, Buyeye said:

It starts with the architecture that allows the house to use the winter sun to warm the walls(and keep the summer sun out), insulation that prevents heat loss(and ventilation to cool the house in summer). Then underfloor heating, geothermal heat pumps are better in places where the air reaches below zero celcius, the normal ones are fine for south africa.

50kwh storage is only 10-12 pylontech up5000 or BYD like in this system 

I would go with a similar system when starting from scratch and budget allowed.

Thanks, Buyeye - we are certainly applying the "Passivhaus" principles as far as we can, and my consumption should drop (apart from the additional EV requirement). -  I'm also thinking that the EVs will be parked in the garage for quite a few hours during the sunlight hours, which will bring my storage requirement (for overnight charging) down, right?

Posted
2 minutes ago, Sats Nkamoto said:

Thanks, Buyeye - we are certainly applying the "Passivhaus" principles as far as we can, and my consumption should drop (apart from the additional EV requirement). -  I'm also thinking that the EVs will be parked in the garage for quite a few hours during the sunlight hours, which will bring my storage requirement (for overnight charging) down, right?

Yes EV's have huge lithium batteries, charging them from pv directly rather then storage will save on storage costs.

Posted (edited)
1 hour ago, Sats Nkamoto said:

Thanks, Buyeye - we are certainly applying the "Passivhaus" principles as far as we can, and my consumption should drop (apart from the additional EV requirement). -  I'm also thinking that the EVs will be parked in the garage for quite a few hours during the sunlight hours, which will bring my storage requirement (for overnight charging) down, right?

Wow, this Sarel knows his bizniz!  Thanks for the pointer!

 

Edited by Sats Nkamoto
Posted
3 hours ago, Sats Nkamoto said:

Wow, this Sarel knows his bizniz!  Thanks for the pointer!

 

Just a pointer on the 120kW required in winter. For a full sun day you need 120/4hrs=30kW of panels. Using 530W panels at 1.1x2.3m each you need 57 panels. This needs about 143 sq m of roof space. You have 90 available.

If you need 120kW in summer you can get 5kW/kW of panels instead of 4kW/kW. This means 45 of the same panels in full sun. This needs about 115 sq m of space. Many days with cloud and rain to reduce the output. Keep this in mind.

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