Pool heating
First of all: It is important NOT TO OVERDO the water temperature in the pool. High pool water temperature can cause illnesses. Microorganisms develop much faster at elevated temperatures.
Secondly: Heat losses are very important (e.g., temperature difference between water and air, thermal insulation of the pool from the ground, pool surface area, etc.). If the ambient temperature is higher than the pool water temp, there will be no heat loss to the air. Losses can still occur to the ground.
Solution 1: using non-pressurized collectors connected to the filtration pump circuit.
Advantages: lowest cost
Disadvantages: Water is heated only when the filtration pump is running (plus a backup of 50l of water in one collector)
Collectors from the MK series, compared to JNSC collectors (and other collectors from various manufacturers based on heat-pipe technology), are made entirely of stainless steel. Also, the heat exchanger in the collective manifold at the top of the collector is stainless steel inside and has a larger connection diameter (1 inch), which allows for greater water flow.
Chlorinated pool water can be passed directly through such a collector (there is no need to build complex heat exchangers and closed systems operating under pressure on glycol solution). Due to the fact that these are non-pressurized collectors, they are much cheaper than those from the SC series (or other collector models from other manufacturers).
The active absorber area of one MK-20 collector is: 2.48 m2 (heating power 1.7 - 2.4 kW - depending on solar radiation, of course)
- To heat 1 liter of water by one degree, 4200J is needed, which is 0.001166666667 kWh.
- To heat 1000 liters of water by one degree, 4200kJ is needed, which is 1.166666667 kWh.
- Using a device with a power of 1200W for 1 hour, we are able to heat 1000 liters of water by 1 degree C.
- If the pool contains 10,000 liters of water (10 m3): to heat it by 1 degree requires 11.66 kWh, meaning a 12kW device will heat it by 1 degree in one hour, while a 1200 W device will heat it by 1 degree in 10 hours.
(the above data are theoretical calculations and do not take into account device efficiency and heat losses)
Assuming for calculations that one vacuum tube of a solar collector has a maximum power of 0.12 kW (in Polish climatic conditions, taking into account device efficiency and solar radiation, the maximum power of a tube ranges from 80 to 100W), one MK-20 solar collector (20 vacuum tubes) will generate about 17 - 20 kWh during a full sunny day, which means it will heat the water in a 10,000 l pool by about 1.5 °C in an hour.
Analogously:
- two such collectors (i.e. 40 vacuum tubes) will raise the temperature by about 3 °C in an hour.
- ten such collectors will raise the temperature by about 15 °C in an hour, etc.
- to heat 10,000 liters of water (10 m3) by 1 °C in an hour, about 120 vacuum tubes (12 kW) are needed
- to heat 5,000 liters of water (5 m3) by 1 °C in an hour, about 60 vacuum tubes (6 kW) are needed
- to heat 20,000 liters of water (20 m3) by 1 °C in an hour, about 240 vacuum tubes (24 kW) are needed
Assuming theoretically 10 hours of sunshine per day, the result is:
- a pool of 5,000 liters of water (5 m3) heated by 10 °C during the day - we need about 60 vacuum tubes
- a pool of 10,000 liters of water (10 m3) heated by 10 °C during the day - we need about 120 vacuum tubes
- a pool of 20,000 liters of water (20 m3) heated by 10 °C during the day - we need about 240 vacuum tubes
- a 24-tube collector will heat a 20,000-liter pool by 1 °C during the day
- a 24-tube collector will heat a 10,000-liter pool by 2 °C during the day
- a 24-tube collector will heat a 5,000-liter pool by 4 °C during the day
The above calculations are only theoretical. Actual results may differ by up to -50%, especially after taking into account heat losses of connection pipes and the pool (both through the surface and side walls)
Solution 2: using pressurized collectors (with heat-pipe tubes), e.g. from the SC series connected to a separate circuit linked to a heat exchanger in the pool.
Advantages: Collectors work independently of the filtration pump.
Disadvantages: Very high equipment cost. Pool water is heated only when the circulation pump is running (without any additional buffer)
The heating capacity of collectors based on heat-pipe tubes (regardless of whether they are our SC series collectors or collectors from other manufacturers) will be comparable to the heating capacity of non-pressurized collectors from the MK series. However, the much higher cost of purchasing collectors, an additional circulation pump, and a heat exchanger in the pool makes this solution the least profitable. The only advantage of such a solution may be the possibility for this system to operate on a glycol solution, which can remain in the installation during winter. When using non-pressurized collectors operating on water, it will be necessary to drain them of water for winter.
Solution 3: using compact non-pressurized collectors from the Solaris-L and YL series.
Advantages: Cost is only slightly higher than when using MK collectors, a large backup of hot water that is dumped into the pool before swimming (which prevents cooling)
- Solaris L-230 (25-tube collector) will heat a 20,000-liter pool by 1 °C during the day
- Solaris L-230 (25-tube collector) will heat a 10,000-liter pool by 2 °C during the day
- Solaris L-230 (25-tube collector) will heat a 5,000-liter pool by 4 °C during the day
The above calculations are only theoretical. Actual results may differ, especially after taking into account the heat losses of the pool (both through the surface and side walls). However, the final effect will be definitely better than with the 1st and 2nd solution, because the solar heater (insulated tank) has significantly lower heat losses than the pool.
In addition to the slightly higher purchase cost of the devices compared to the first solution, we obtain a number of other benefits:
- a large stored hot water buffer that does not cool down during the day and is "dumped" into the pool before swimming
- the system does not constantly burden the filtration pump (collectors are emptied by gravity, filled once a day using a separate pump or using the filtration pump)
The energy balance (also when using a 20-tube solar collector) will be the same as in the first solution, but we will avoid unnecessary cooling of the water. For example, you can heat the water in the pool at night or in the morning (which will be impossible in the case of the first or second solution).