Solar panel sizing

T

tipperary

Registered User
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Hi all
recently moved into our house, and have some queries about the solar installation. The builder installed two 2m2 panels (combined effective area 3.5m2), and a 500 liter tank. The spec called for 5m2 effective area of panel and a 400 liter tank. Anyway, the panels are not working as great as I had hoped, just getting into the mid 40's on a sunny day.

Basically, I am wondering if I should double up on the panels. We would like the panels to be sized properly for 5 to 6 adults. Part of the reason for sizing the tank at 500 liters may be because it is a heat dump for the back boiler on the solid fuel stove.

Any help would be appreciated.
 
Looks like your hot water storage cylider is oversized even with a stove/boiler connected. The norm is to allow 50/60 litres per person with 1m2. Therefore 4m2(2 panels) = 200/240litres = 4 person. To achieve adequate cylinder temperatures you will need to install another panel(2m2) at least. Your two existing panels just don't have the capacity to heat all that water up. your 500litre cylinder will be more than adequate for 5/6 people. Hope this helps
 
I am putting in a solar system next week and we are putting 5m2 of tubes on the roof with a recommended 250ltr triple coil tank. One coil for the oil central heating, one for the solid fuel stove and the last one for the solar tubes.
 
I have a 450 liter tank ( dual coil with 4 solar panels 2 meters wide x 1.8 in length) 100 tubes in all . We have a long run from the panels to the cylinder ( 25 meters in each direction)
The tank gets to 58C or 60 C on real sunny days.
 
ruffmut, your solar system capacity is spot on. Just make sure that your solid fuel stove/boiler has a unrestricted (no valves etc) 25mm diameter primary circuit to one of the three coils and this circuit is open vented.
 
i agree with villa1 that To achieve adequate cylinder temperatures you will need to install another panel(2m2) at least.
 
500 litre tank is massive, I would have thought 300 litre tank better for fmaily of 5-6 with 5m2 panels. Now you have th tank in add the panels did you get the grant?
 
Hi there

I missed out on the grant as the builder incurred delays which meant the panels were not installed within 12 months of getting the grant approved. got the money knocked off the price from the builder though so worked out OK that way.
 
so you should be able to get the grant now by reapplying for the extra panels?? 2 panels 4m2 should get you 1000 euro grant and cost around 1600 plus install...
 
Hi Marcole

I looked into that. Unfortunately I would need to be in the house for 12 months before I would be eligible for the grant. I don't really want to wait this long as I am afraid the panels I have could be discontinued by then. The fact that I previously applied for a grant means that SEI know the house was not completed until February last at the earliest.
 
ok, you can use different solar panels in one system. Basicaly the panels are just heat exchangers so you can have a mixture of flat and tubes if you want its just up to the cosmetics..yeah the grant is out if you need before then, but otherwise just wait....
 
Just looking for advice on sizing for 2 adult and 4 teenage kids who play lots of sport so have lots of showers morning and evening.

Would a 300litre tank be enough or should I go for a bigger tank with lots of tubes??
Going for tubes for performance over flat plate - probably Ritter

Thanks
RB
 
If you are seriously looking at buying a Ritter system then you will not be disappointed, we fitted 7 x 6 tube panels into a 500 litre cylinder, high usage all day and the system keeps recovering the heat to the cylinder. Even this week its displaying 58 > 60 C. We are glad we fitted a heat dump because I reckon the system will be under pressure from the heat generated on sunny days. A good guide for the cylinder in domestic systems is 50 litres per person, of course a lot depends on lifestyle, for example power showers use more hot water than a standard shower, hot water being drawn all day instead of morning and evening etc. Wishing you well with your system.
 

i've solar panels and my view is the most important thing to determine how many panels are needed is the orientation of the house. we had a clown come out and spec ours, he told us we were south west and needed 40 tubes and a 300L tank, turns out we were due west facing and needed 60 tubes to work with the 300L tank, with the 60 tubes we're getting between 45-55 degrees most days
 
Seriously looking at the following Solar water heating system
Requirements - daily showers for 6 people. Showers are powered by a showermate pump.

System - Grant Engineering
3 X Solar collectors (Aurora panel)
1 X 300L triple coil (only need two, adding spare for future)

I know where a couple of these systems were installed and feedback is good, however nobody has gone to the effort of calculating savings to determine ROI.

Thoughts anyone?
 
We normally use Tsol software modelling or similar to calculate the contribution of the system based on data from its EN certs and other data about the roof angle and orientation, location, pipe dimensions, size of solar cylinder etc. I can give you a model in relation to panels that we work with on that, and I would imagine that your supplier should be able to do likewise.

ROI really depends though on the cost of the hot water it is replacing, and how you are obtaining that presently. You will also have some savings from improved insulation in the new cylinder. Oh - and how much your system is costing you...
 
Part of the problem is to know what to ask for, have not heard of a modeling tool (though I did think something like that should exist) and therefore did not ask, so I would greatly appreciate any assistance.

As for obtaining hot water now - that's by an oil fired boiler, also have an immersion though its rarely used.

Still getting pricing on systems but am thinking in the range of 3.5-4k

Thanks for your help quentingargan
 
There is free software from Retscreen which is very good, though it is for a variety of renewables. If you are into the challenge, it is a good tool to work with and learn from, based on Excel.

We use Tsol which is a specific solar water heating modelling software. If you want to PM me what part of the country you are in, roof orientation and slope, rough idea of water usage (number of people, whether you use baths, showers or power showers etc.), and distance from panel to cylinder, I could email you an estimate of savings. Q
 
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