Solar thermal project for washing station

[marin75]

Hello everybody
I am currently carrying out a feasibility study on the installation of thermal sensors on the roofs of several car wash stations in France for the blue elephant group.
However, I come up against several problems because the consumption of the stations differs from the "classic" consumption, and I lack knowledge (which is difficult to find on the internet !!). Let me explain :
Take the example of a station at dawn. It consumes an average of 42 kWh / year of gas (with the ENGIE conversion system). The station roofs are 000m ^ 90 (2x18) and are horizontal (with the possibility of tilting the row of panels facing south over the entire length). The current boiler operates on gas.
After several in-depth researches I started a study with the characteristics of different panels but I cannot size my water heater which must meet very specific criteria. The station requires an average of 2600L of hot water per day and the heating of the water must be rapid to ensure a regular and spontaneous supply on big days. Which water heater would be suitable? Should we start by sizing the water heater or the surface of the collectors?
I had also started my study by maximizing the number of possible panels to fill the entire length of the roofs, but realized that the performance did not increase if we exceeded a certain number of panels mounted in series. Is it profitable to maximize the roof area knowing that the energy demand is very high? if so, do we need a water heater using a battery of sensors or can we centralize everything in one?
Voila voila, I'm a bit of a blur at the moment and would need a lot of help to guide me in my study!
A big thank you to everyone who takes the trouble to answer me,
Marine

[Macro]

The station consumes 2600 liters of water per day ... But it does not heat all this quantity .... The rinses buffings ... Being made with cold water ...

What type of boiler is ... Does it heat a buffer tank or heat it immediately if needed like a classic hot water karcher?

For me it is necessary to evaluate the quantity of daily hot water consumed (number of average washing cycles x time x flow) size the heat exchanger for this quantity ask the maximum of solar collectors that allows the surface of the roof then the boiler (if it is heating on demand) will need less power to heat the water .... on sunny days ... The ecological issue could be important but the economic profitability of the installation will be made on a depreciation of very long lasting ...

[marin75]

Thank you for this quick response,
So on average a wash of 10/15 min requires 20L of HOT water. The station with 4 tracks, if these run full speed for 5/6 hours (generally this is not the case but the station runs about 10 hours per day). You get an average fairly easily and you quickly get the necessary 2500L of HOT daily water.
To be more precise, here is a first draft that I tried to produce using TechSol software.
I would have liked to know if this "pre-study" already seems realistic (before going into the economic aspects). As said previously, I am wondering about the possibility of optimizing the operation, in this example, of my 8 thermal sensors if they are in series, and then on the sizing of the storage system (tank) which to my opinion is undersized in this case.
I take this opportunity to ask 2 other questions: Is it possible to have an approximation of the heating time of a balloon (let's take the example of a 1000L with the optimal number of associated panels) in the idea of ​​providing quickly to the needs and renew the water heating several times a day?
Then, in the case of this kind of installation would it be wise to replace the existing tank with a solar water heater with an additional, for example electric, directly in it (solar exchanger at the bottom of the tank and electric water for example) to optimize the place of the technical room?
Merci!

PS: the first screen corresponds to viessman 30 tube sensors which were not in the TECHSOL database, so I had to choose 24 tubes in the software.

[Macro]

Is the study done for the creation of a new station or the optimization of an existing station? because it changes everything about the design ...

For me it will need anyway energy supplement (gas or oil electricity) or a phenomenal dimension of the installation for a period of limited use ... The irregular nature of consumption seems to me a great difficulty for the study ....

In my humble opinion the solar in the case of this kind of installation should more be a means of preheating the water with then a definitive heating by the classic boiler which according to the case will heat more or less ...

After the calculations ... I can not answer you better than the documentation of suppliers of this kind of material ...

No doubt here you will find more competent people than me ...

[chatelot16]

it would be absurd to build a huge surface of solar collector to make the total energy which there is need some day ... these enormous collector would not be profitable every day, and even often useless

you have to choose a fairly low collector power, which will pay off as much as possible, because even on days when the station is not very frequent all the heat will be useful ... and the rest will be heated by the usual means

it is necessary to build in a modular way: start with a low solar power, measure and record, and increase the surface of the panel if the measurements indicate that it is useful ... especially not to make a first installation with too large surface not profitable which ridicules the idea of ​​solar heating

for a network like blue elephant it is better to start from the solar panel on a large number of stations where it will be 100% useful than to put too much on a single station where it will not often be used 100%

[marin75]

Your advice is noted!
The study is done on an already existing station, the idea was to put 1 row of panel on the roofs in south orientation with an optimal slope of (between 35 and 45/50 I still have to determine it).
Then as regards oversizing, I agree with you on the whole, with such consumption I had not taken into account the off-peak summer days or a very large installation would be obsolete.
I would like to take this opportunity to ask you my last question: in 2017, is it more profitable to invest in tube or vacuum tube collectors? for an installation like these would you have advice? I have not yet contacted a supplier to have a price range but I have seen the coefficients of the 2 types of panels by noting that the tubulars are more efficient but do they justify a price almost double in view of their performance (performance also doubled)?
Thank you all!

[Macro]

Considering the "free unattended access" character of the installation .... Personally I will opt for the less coveted and less fragile panels .... And I would keep a little room for a photovoltaic surface which would supply the pump of circulation of the heat transfer fluid ... As that it would turn only when it would need to turn ... thus limiting the sensors and automatisms to be implemented ...