Performance Evaluation of Solar Still.

Introduction

The increasing demand for clean and safe drinking water has created a need for sustainable and energy-efficient water purification technologies. Conventional water purification methods often require significant electrical or thermal energy, which increases operating costs and environmental impact. Solar energy, being abundant and renewable, can be effectively utilized for thermal applications such as water purification and desalination. A solar-based distillation system utilizes solar thermal energy to heat water, generate vapour, and subsequently condense it to obtain purified water. The performance of such a system is influenced by factors such as solar radiation intensity, water temperature, ambient temperature, and condensation conditions. Therefore, monitoring these parameters is essential to evaluate the system performance and understand the relationship between solar energy availability and freshwater production.

Concept/Methodology-

• Utilization of solar thermal energy for water purification.
• A parabolic solar collector concentrates sunlight at the focal region.
• Concentrated solar energy generates heat and increases the water temperature.
• Increased water temperature promotes evaporation.
• Water vapour condenses on a relatively cooler surface.
• The condensed water is collected as distilled water.
• The study focuses on the relationship between:
  • Solar radiation / light intensity
  • Water temperature
  • Distilled water output
• Readings are recorded at regular time intervals to evaluate system performance under varying solar conditions.

11/09/2026 to 15/09/2026

Discussion with Dixit Sir-

On 11 September 2026, temperature readings of the solar still were recorded at regular time intervals. The initial temperature at 10:07 AM was 25.5°C, and the temperature increased with solar heating, reaching a maximum of approximately 67°C at 4:20 PM.

After recording the temperature data, the readings were discussed with Dixit Sir. During the discussion, Sir asked an important question: “How much water was evaporated during the experiment?” At that stage, the amount of evaporated water had not been measured.

Based on this observation, the following parameters were suggested for recording during the next solar still experiment:

• Initial quantity of water added to the solar still
• Final quantity of water remaining after the experiment
• Amount of water evaporated, calculated as:
  Water evaporated = Initial water quantity − Final water quantity
• Light intensity (Lux) during each observation
• Cloudy/clear weather conditions
• Temperature of the solar still at regular time intervals

These additional parameters will help in establishing a better relationship between temperature, light intensity, weather conditions, and water evaporation, and will provide more meaningful data for evaluating the performance of the solar still.

DATE- 18/09/2026

Data Collection and Observation

During this trial, the variation in light intensity and water temperature was monitored at 30-minute intervals from 11:00 AM to 5:30 PM. Light intensity was recorded using a lux meter, while water temperature was measured at the corresponding time intervals. A significant reduction in light intensity was observed at 2:30 PM due to cloudy conditions, followed by an increase after the clouds cleared. The water temperature generally increased with solar exposure and reached a maximum recorded value of 45°C at 5:00 PM.

However, an independent effective/ambient temperature was not recorded during this trial. Therefore, the present analysis is limited to the relationship between light intensity and water temperature. Future trials should include ambient temperature and other relevant solar-still parameters for a more complete performance analysis.

DATE- 19/09/2026

The trial showed a general relationship between solar light intensity and water temperature. The water temperature increased during the period of higher solar exposure and reached a maximum of 47.5°C at 12:30 PM. After the occurrence of cloudy conditions, light intensity decreased considerably, followed by a gradual decrease in water temperature.

DATE- 20/09/2026

Since the temperature of 5 L of water was not increasing sufficiently, a trial was conducted using 1 L of water to observe the temperature variation more effectively. Before conducting the trial, the plates of the solar still were cleaned to improve the absorption and trapping of solar radiation. The readings of water temperature and light intensity were recorded at regular time intervals.

TIME	WATER TEMPERATURE in degree C	LIGHT INTENSITY (in LUX)
11:00	32	50200
12:00	45.4	90000
12:30	46.2	28100
1:00	47.1	55100
1:30	43	15000
2:00	36.3	16800
2:30	37.4	15000
3:00	38.6	13400
3:30	40	35700
4:00	42.7	30000
4:30	42.1	25700
5:00	37.1	15000

The water temperature in the solar still reached a maximum of 47.1°C at 1:00 PM. However, the temperature did not consistently follow the light intensity, suggesting that other environmental and system-related factors may influence the heating performance

DATE-11/10/2026

On 11 October 2026, a trial was conducted to evaluate the performance of the solar still using 2 litres of water. The water temperature and light intensity were recorded at regular time intervals to study the effect of solar radiation on water heating and evaporation.
During the experiment, the water temperature increased gradually from 27°C at 11:00 AM to a maximum of 60°C at 2:00 PM. After 2:00 PM, the temperature decreased gradually and reached 36°C by 5:00 PM. Although the water temperature increased during the peak heating period, the expected evaporation was not observed. This indicated that the system’s heating performance under the tested conditions needed further investigation. The recorded readings of water temperature and light intensity are presented in the following table.

Time	Water Temp. °C	Light Intesity
11:00	27	30000
12:00	40	69000
1:00	48	68600
2:00	60	56000
3:00	50	45200
4:00	38	42000
5:00	36	31200

This trial on 2 liter water.

Conclusion-

The maximum water temperature achieved was 60°C, despite an average light intensity of approximately 70,000 lux. The limited heating may have affected the evaporation rate. Possible reasons include reduced solar radiation transmission due to the damaged transparent sheet and leakage between the basin and conical cover. Further inspection is required to identify the exact cause and improve the solar still’s performance.