This refers to passive solar collector, where solar radiation is used to heat water. It is therefore not on the solar cells.

What characteristics should solar collectors have, to function in an optimal way?
Why should these properties be fulfilled?

If there is a water flow of 500 g / minute to a solar panel on one m2, how much water is heated up under optimal conditions during the passage of the collector? Expect that the collector is in Gothenburg and the calculation is done for one day in mid-June (noon)

The characateristics? Incoming radiation should not be reflected, but absorbed. Having the panels black (non glossy) helps greatly. The panels should automatically dumped of water when freezing temperatures are present. So this presents a problem, how can one collect heat in freezing days? Answer: the collector should be covered with a transparent (glass) which does not reflect radiation. Water should not be circulated when the temperature inside the collector is less than water temperature. So what I am suggesting, is that controls be automatic. Finally, the collector should be isolated from cold winds, but pointed directly at the Sun during the day. If possible, it can move with the sun's path, but generally, that is to difficult, so point it at the sun during mid afternoon.

heat gained: Area*solar flux*time

How much water? flow rate*time

ok but what is solar flux and should i assume that time is 24 hours?

You need to look up the solar radiation at that location. Then, look to see how many hours of radiation is supported. In june, one probably can get about 6 hours of effective radiation, but you will find tables for this. No, not 24 hours, you cant get radiation during the night. I have seen tables where solarflux*time is actually tabulized as a product, so you don't have to look up each.

I just found the following: I didn't find any time tables

I still need help

Regards
Solar radiation on Earth: As the Sun's energy spreads through space its spectral characteristics do not change because space contains almost no interfering matter. However the energy flux drops monotonically as the square of the distance from the Sun. Thus, when the radiation reaches the outer limit of the Earth's atmosphere, several hundred kilometers over the Earth's surface, the radiative flux is approximately 1360 W/m2

To function optimally, solar collectors should have the following characteristics:

1. Absorption: Solar collectors should have a high absorption rate for solar radiation. This means that they can efficiently absorb the sun's energy and convert it into heat. Typically, a dark-colored surface or materials with high thermal conductivity are used to enhance absorption.

2. Thermal Insulation: The collector should have good thermal insulation to minimize heat loss to the surrounding environment. This is typically achieved by using materials with low thermal conductivity and adding insulation layers to minimize heat transfer.

3. Low Heat Loss: Solar collectors should have minimal heat loss to maximize overall efficiency. This can be achieved by using materials with low thermal conductivity, optimizing the design to reduce heat transfer, and incorporating glazing or cover materials to trap heat.

4. Transmittance: The glazing or cover material of the collector should have high transmittance to allow solar radiation to pass through easily. This ensures that more sunlight reaches the absorber and maximizes heat generation.

5. Durability: Solar collectors should be durable and resistant to weather conditions, such as temperature variations, humidity, and UV radiation. This ensures a longer lifespan and efficient operation over time.

These properties need to be fulfilled because they contribute to higher energy conversion efficiency, resulting in more effective heating of the water. By maximizing absorption and minimizing heat loss, solar collectors can produce more heat from the available solar radiation, leading to better energy utilization.

Now, let's calculate how much water would be heated up under optimal conditions during the passage of the collector:

Given:
Water flow rate = 500 g/minute = 0.5 kg/minute = 0.5/60 kg/second
Collector area = 1 m²

To calculate the amount of heat transferred to water, we need to determine the change in temperature and the heat capacity of water.

Assuming the water is initially at the ambient temperature of Gothenburg in mid-June (noon), let's consider it to be around 25°C.

The specific heat capacity of water is approximately 4.18 kJ/kg°C.

To calculate the amount of heat transferred, we can use the formula:
Q = m * c * ΔT,

where:
Q = Amount of heat transferred
m = Mass of water
c = Specific heat capacity of water
ΔT = Change in temperature

By substituting the given values, we can solve for Q.

Q = (0.5/60 kg/s) * (4.18 kJ/kg°C) * (ΔT)

To find ΔT, we need to consider the temperature rise due to solar radiation incident on the panel. The amount of temperature rise will depend on the efficiency of the collector in converting solar radiation to heat.

Let's assume the collector has an efficiency of 70%.

Therefore, ΔT = (Amount of solar radiation incident on the panel) * (Collector efficiency) / (Heat energy needed to increase the temperature of water by 1°C)

The amount of solar radiation incident on the panel can be determined based on the solar insolation data for mid-June in Gothenburg. Specific insolation values can be obtained from weather records or solar energy databases.

Once you have the insolation value, you can calculate the heat energy needed to increase the temperature of water by 1°C using the formula:
Heat energy = m * c

Substituting all the values and calculating, you can find the amount of water heated up under optimal conditions during the passage of the collector.