What About Solar Energy in Aquaculture | 3 Common Misconceptions

Scientific layout can reduce summer water temperature by about 3℃, decrease water evaporation by 25%, and effectively inhibit harmful algae.

Combined with a professional-grade multiple leakage protection system, it not only ensures fish safety but also generates an extra income of thousands of currency units in electricity fees per acre.

This model is technologically mature and industry-recognized, making it an authoritative aquaculture solution that balances ecological protection with high economic benefits.

Shading Kills Fish

How much sunlight remains

Photosynthetically Active Radiation (PAR) is between 400 and 700 nanometers, which is the physical basis for maintaining pond primary productivity.

Under full light conditions, the surface light intensity often reaches 100,000 lux, while the light compensation point for most phytoplankton is only 500 to 1,000 lux.

When the photovoltaic panel coverage is set between 35% and 45%, the transparent areas and scattered light still provide 40,000 to 55,000 lux of effective light intensity for the water, which is more than 3 times higher than the saturation light intensity of algae.

Research records show that at a water temperature of 25 degrees Celsius, the photosynthetic rate at a depth of 0.8 meters can be maintained at 92%, ensuring that each unit volume of water produces more than 3.5 mg of endogenous oxygen per hour.

· Light utilization: The back of bifacial modules can reflect 10% to 15% of light to the water surface, compensating for a 5% loss of direct light.

· Translucent spacing: Leaving a net spacing of 6.5 meters between panels ensures that 70% of the water surface receives direct light in rotation within 8 hours a day.

· Compensation mechanism: By configuring a 1.5 kW impeller aerator, with a single unit covering 8 acres of water surface, the mechanical oxygenation can be stabilized at around 6.0 mg/L.

How many degrees does the water temperature drop

High-intensity light causes surface water temperatures to rise rapidly to over 34 degrees Celsius, exceeding the optimal growth threshold of 28 to 30 degrees Celsius for most economic fish.

After installing 550 W+ monocrystalline silicon modules, the shading effect in the area under the panels reduces the water temperature at a depth of 50 cm by 3.2 to 4.8 degrees Celsius.

For every 1 degree Celsius drop in water temperature, the physical saturation of dissolved oxygen increases by 0.15 mg/L, which means the actual dissolved oxygen capacity of the water in the shaded area is increased by more than 0.6 mg/L at noon in summer.

For temperature-sensitive sea bass or rainbow trout, the mortality rate induced by heat stress dropped from 7.5% to < 1.2% as the temperature fluctuation within 24 hours narrowed from 6 degrees Celsius to 2.5 degrees Celsius.

· Evaporation loss: Shading reduces water surface evaporation by 22%, saving 150 to 200 cubic meters of fresh water supplement per acre of pond annually.

· Enzyme activity balance: The metabolic rate of fish at 29 degrees Celsius is 25% more stable than at 35 degrees Celsius, and the efficiency of intestinal digestive enzymes is improved by 18%.

· Water level fluctuation: Maintaining a constant water level of 1.8 meters to 2.2 meters, with bottom pressure maintained at 18 to 22 kPa, helps maintain the osmotic pressure balance of fish.

Is there enough oxygen

It is a misconception that shading causes severe hypoxia; however, 80% of hypoxic deaths occur between 3 AM and 6 AM, when no photosynthesis takes place.

In a system with 40% PV coverage, the nighttime dissolved oxygen decline rate monitored by sensors in real-time is 0.35 mg/L per hour, which is 16% lower than the 0.42 mg/L decline rate in open ponds, reducing oxygen consumption pressure.

This is because shading inhibits the over-proliferation of cyanobacteria by more than 30%, reducing the intense competition for oxygen by algal respiration at night.

Measured data shows that automated systems equipped with smart sensors automatically start when dissolved oxygen drops to 4.5 mg/L, saving 20% to 28% in aerator electricity costs compared to traditional manual judgment.

Monitoring Indicators	Shaded Zone Values	Open-air Zone Comparison	Data Interpretation
Min DO at dawn	4.8 mg/L	3.9 mg/L	The shaded zone fluctuation is smoother.
Ammonia concentration	0.15 mg/L	0.45 mg/L	Reduces ammonia produced by decaying algae.
pH variation	7.6 - 8.1	7.2 - 9.1	Inhibits violent photosynthetic fluctuations.
Hydrogen sulfide	< 0.01 mg/L	0.05 mg/L	Bottom organic matter decomposition rate reduced by 15%.

Growth speed

The Feed Conversion Ratio (FCR) of fish directly determines 60% of the operational budget expenditure.

In a semi-shaded environment, the hidden space provided by photovoltaic panels simulates the natural predator-avoidance environment of fish, reducing their kinetic energy consumption by 10% to 15%.

Comparing a 12-month breeding cycle, the average weight of a single fish raised in the shaded area increased by 120 grams, and the growth rate was 14.5% faster than the full-sun control group.

This means that for the same 1.5-pound specification, shaded breeding can be marketed 20 to 35 days in advance, and the capital turnover rate is increased by more than 8%.

For Tilapia, the feed coefficient was optimized from 1.55 to 1.38, and the feed cost per ton of adult fish was reduced by 900 to 1,200 currency units.

The survival rate per 10,000 fingerlings under the photovoltaic system is usually stable above 93%, which is a significant improvement compared to 86% in open-air farming.

This difference stems from 20% of ultraviolet (UV) light being absorbed by the baffles, protecting the epidermal mucus layer of the fry from burns and reducing the probability of white skin disease by 45%.

At the same time, the photovoltaic support structure provides 150% additional attachment area for beneficial epiphytic algae, which increases the nitrite removal rate in the water by 22.5% through biological filtration.

How to arrange the panels

The array design of photovoltaic panels must strictly match the span of 5 meters to 8 meters to ensure that the operation redundancy of fishing nets between the supports reaches more than 1.5 meters.

The pile foundation adopts PHC pipe piles with a diameter of 400 mm and a compressive strength of 80 MPa, with a displacement deviation of less than 15 mm under a 12-grade wind load.

The lowest point of the bracket bottom from the water surface needs to be maintained at 2.5 meters, which reserves a 1.2-meter water level fluctuation space and a 1.3-meter fishing boat operation height.

For a project with a single capacity of 1 MW, it is recommended to configure 10 sets of 0.75 kW microporous aeration equipment, with a distribution density of one set per 3 acres, to eliminate a possible 10% dissolved oxygen blind zone under the photovoltaic panels.

· Angle optimization: A tilt angle of 15 to 25 degrees not only improves power generation efficiency by 8.5%, but also uses rainwater to automatically wash away 60% of surface dust.

· Desilting strategy: Air-lift sludge suction every 3 to 5 years, with suction pressure controlled at 0.5 MPa, can effectively remove organic sediment 20 cm thick.

· Cable specifications: Use 4mm² DC dedicated PV cables, controlling the voltage drop within 100 meters transmission distance to within 1%, ensuring power conversion efficiency remains above 98.5%.

High Maintenance Danger

Is the pile foundation stable

The structural safety of Fishery-Solar complementary power stations begins with accurate verification of underwater pile foundations.

In aquaculture waters with a depth of 2.5 meters to 4.0 meters, pile foundations usually use Prestressed High-strength Concrete (PHC) pipe piles with diameters of 400 mm to 600 mm, and their compressive strength grade is not lower than C80, ensuring no structural settlement occurs during the 50-year design life cycle.

According to fluid mechanics simulation, when the gust wind speed reaches 38 m/s (approx. 13-grade wind), the horizontal shear force sustained by a single pipe pile is about 15 to 22 kN, while the design margin of modern bracket systems is usually set at more than 1.5 times.

The surface of the bracket adopts a metal coating with a thickness greater than 85 microns. In a high-humidity water surface environment with a salt content of 3%, the annual corrosion rate is controlled below 0.01 mm. This material characteristic ensures the entire system does not require large-scale structural replacement during the 25-year operation period.

Core Parameter Indicators:

· Single unit load capacity: Each group of brackets can carry 28 to 32 pieces of 600W+ modules, and the static load standard must reach 5400 Pa.

· Wind resistance displacement: Under extreme weather conditions once every 50 years, the horizontal displacement deviation of the top of the pile foundation must be controlled within 20 mm.

· Bracket material: Use aluminum-magnesium-manganese-zinc coated steel, and its salt spray test duration must exceed 3,000 hours.

Is cleaning the panels tiring

For a 10 megawatt (MW) scale water surface power station, the labor intensity of manually cleaning 18,000 PV panels is indeed extremely high, but modern projects have fully popularized automated maintenance.

Using crawler or self-propelled cleaning robots, a single machine can complete 300 to 500 square meters of cleaning tasks per hour, keeping the light transmittance of the module surface above 98.5%.

Experimental data shows that performing automated cleaning once a month can increase power generation revenue by 3% to 5.5%, while the water consumption per single cleaning is only 0.5 liters per square meter.

Due to the 15 to 20-degree tilt design of the PV array, when the rainfall exceeds 10 mm, about 70% of the surface dust can be removed by the rainwater self-cleaning function, which reduces the frequency of deep manual intervention to 2 to 3 times per year.

Maintenance Efficiency Data:

· Robot operation: A single robot can cover an installed capacity of 5 MW to 8 MW, and the cell life must support continuous work for 6 to 8 hours.

· Power generation gain: Removing the 2 cm ash accumulation belt on the lower edge of the module can prevent local hot spot effects and extend module life by more than 15%.

· Water cost: Using filtered pond water for recycling, the annual cleaning water budget per MW is lower than 150 currency units.

Is fishing difficult

Standard Fishery-Solar design sets the row span between 6.5 meters and 10.5 meters, which leaves sufficient operation space for automated aeration boats and feeders with a width of 3.5 meters and a draft of 0.8 meters.

During the fishing stage, traditional net-pulling operations are replaced by modular fishing systems. The 2.5-meter net clearance reserved at the bottom of the bracket ensures that personnel still have 1.0 meter of activity range in 1.5-meter deep water.

Statistics show that the fishing efficiency under this structural layout is only 8% to 12% lower than that of open-air ponds, but by installing an automatic sensing feeding system on the brackets, the feed distribution coverage per acre can reach over 95%, reducing feed waste by 10%.

Spatial Layout Specifications:

· Vertical clearance: The lower edge of the PV panel must be kept more than 2.0 meters above the historical highest water level to meet ventilation and boat travel needs.

· Pile spacing: The horizontal pile spacing is usually 4.5 meters to 6.0 meters, ensuring that the net is not obstructed by the pile foundation during the dragging process.

· Mechanization rate: After integrating the smart fishery system, the breeding area managed by a single person can increase from 20 acres to more than 150 acres.

How to repair when broken

Highly reliable electrical equipment significantly reduces the frequency of on-site maintenance. The mean time between failures (MTBF) of modern string inverters has exceeded 100,000 hours, and the protection level reaches IP66, which can completely resist the erosion of water mist and splashes on the water surface.

Through the SCADA monitoring system, maintenance personnel can obtain more than 40 operational data points such as current, voltage, and branch temperature every 5 seconds.

When the system detects that the DC side insulation resistance is lower than 50 kΩ, it will automatically trigger an alarm and pinpoint the fault to a specific PV string.

This predictive maintenance model compresses unplanned downtime to within 0.1%, and the workload of on-site inspection personnel is 45% lower than that of traditional ground power stations.

System Monitoring Parameters:

· Fault location accuracy: AI-based IV curve scanning technology can achieve 100% string-level fault diagnosis, with identification error less than 1%.

· Spare parts turnover: The modular design of core modules such as junction boxes and combiner boxes shortens a single replacement time to within 15 minutes.

· Communication stability: Using an optical fiber backbone network overlaid with 5G wireless coverage, the data transmission delay is controlled below 100 milliseconds.

Is it labor-intensive

For a standardized water-surface PV breeding base, the annual maintenance labor cost per MW only accounts for 0.8% to 1.2% of the total investment.

Since the PV brackets themselves provide a ready-made power and network carrier, the installation costs of monitoring cameras, water quality sensors, and automatic aerators are reduced by 30%.

Data shows that after adopting the smart inspection system, the frequency of manual pond inspections was reduced from four times a day to once a week, and the labor cost expenditure per 10,000 pounds of fish was reduced by 22%.

In the financial model, although the initial EPC cost increased by 15% to 20%, the overall project payback period can usually be stabilized between 7.5 and 9.2 years through electricity fee offsets and labor optimization.

Economic Benefit Estimation:

· Labor hours: The average daily maintenance time per 100 acres of water surface decreased from 12 man-hours to 3.5 man-hours.

· Energy consumption optimization: PV direct power is used for aeration and feeding systems, which can save 100% of daytime breeding electricity costs, saving about 400 currency units per acre per year.

· Insurance rate: Due to the high-standard wind resistance design and real-time monitoring, the comprehensive property insurance rate for such projects is usually maintained between 0.15% and 0.25%.

Lower Yields

Is the yield high

In a full-sun environment, the surface light intensity at noon between 11 AM and 3 PM in summer usually exceeds 100,000 lux. This excessive radiation causes fish to enter a stress state, with cortisol levels increasing by 40% to 60%.

After installing a PV system with 45% coverage, the average light intensity at the water surface stabilizes at 35,000 to 50,000 lux, which is exactly within the optimal range for photosynthesis and visual feeding for most economic fish.

Experimental comparison shows that during the 180-day breeding cycle, the yield per cubic meter of the PV pond reached 18.5 kg, which is 14.2% higher than the 16.2 kg of the open-air control group.

This increase in yield stems from the optimization of fish energy allocation. Since the shaded area reduces ineffective swimming energy consumption by 15%, fish can convert 35% of ingested protein into muscle tissue, while this conversion rate in traditional ponds is only 28%.

In the constant temperature layer of 28 degrees Celsius, the Specific Growth Rate (SGR) of fish increased from 1.1% to 1.25% daily, which means that the time to reach a marketing specification of 1.0 kg can be shortened by 15 to 22 days.

Fish become heavier

The average weight and meat firmness of adult fish are directly determined by the Feed Conversion Ratio (FCR). Under the PV panels, because the water temperature fluctuation narrowed from 6.5 degrees Celsius to 2.8 degrees Celsius daily, the activities of protease and lipase in the fish intestines remained at peak levels above 92%.

Data shows that the FCR of Tilapia under the shading system was 1.35, while the open-air group was 1.52. This means that for every 1,000 kg of adult fish produced, the PV system can save 170 kg of feed. Calculated at 1,200 currency units per ton of feed, the unit production cost is reduced by 11%.

Growth Indicators	PV Shaded Zone	Open-air Control Zone	Data Difference
Average weight (g)	850	720	Increase 18.1%
FCR	1.35	1.52	Optimize 11.2%
Survival rate (%)	94.5	86.0	Increase 8.5%
Fatness (K-value)	2.15	1.92	Increase 11.9%

High-density PV arrays do not compress the living space of fish; instead, they increase the aquatic biomass by 20% through the support structures, providing additional natural food for the fish.

Monitoring found that the size uniformity of adult fish in PV ponds at harvest increased by 15%, and the coefficient of variation (CV) for weight dropped from 12% to below 7%, leading to a market acquisition premium of 5% to 8% for single batches of products.

Water becomes stable

Yield decreases are often caused by mass mortality due to deteriorating water quality, while the inhibitory effect of PV panels on algal blooms plays a yield-stabilizing role.

The PV system blocks 50% of ultraviolet radiation, reducing the chlorophyll-a concentration in the pond from 150 mg/m³ to 85mg/m³, effectively preventing extreme low-oxygen events below 0.5 mg/L caused by summer cyanobacteria blooms.

Measured data shows that the ammonia nitrogen concentration (NH3-N) in the shaded area remains stable at 0.12 mg/L for a long time, which is 35% lower than that in open ponds, directly reducing the risk of respiratory system damage by 20%.

Since, for every 1 degree Celsius drop in water temperature, the physical dissolution capacity of oxygen in the water increases by 2.5%, the dissolved oxygen reserve (DO) under the PV panels is 0.8 mg/L higher than that in the open-air area at noon in summer.

This stable dissolved oxygen environment supports a higher stocking density, from 2,500 fish per acre to 3,100 fish, increasing the system load capacity by 24%.

At the same time, the range of water pH fluctuation narrowed from 7.0-9.2 to 7.5-8.3, avoiding chemical burns to fish gills in highly alkaline environments.

How much is saved

By reducing the photochemical reaction rate by 25%, the PV system slows down the decomposition rate of organic matter at the bottom of the pond, reducing the concentration of hydrogen sulfide (H2S) by 40%.

Due to the increase in water transparency by 12 to 18 cm, the frequency of water quality warnings monitored by managers through automatic sensors was reduced by 30%, and the annual chemical input cost per acre dropped from 600 to 420 currency units.

Operating Efficiency Parameters:

· Electricity cost: Aerator running time reduced by 18% to 22% due to lower water temperature.

· Water change frequency: Evaporation reduced by 20%, saving 180 cubic meters/acre in annual water supplement.

· Disease incidence: Heat stress-induced bacterial diseases reduced by 45%.

· Management hours: Automated monitoring coverage is 100%, and the frequency of manual inspections is reduced by 50%.

During the 25-year operation cycle, the comprehensive output per acre of water surface (including electricity income and fishery growth) is 4.5 times higher than that of the pure breeding model.

Even without counting power generation income, relying solely on the improved 8.5% survival rate and 11% feed efficiency, the payback period for farmers can be shortened from the traditional 4.2 years to about 3.5 years.

Spacious clearance

Concerns about supports affecting fishing and leading to yield reduction have been resolved through large span designs of 7.5 meters to 8.5 meters.

This spacing allows 1.5-meter wide automatic fish suction pumps or 2.0-meter wide modern trawlers to pass unimpeded at a speed of 1.2 knots, with fishing loss rate controlled within 0.3%, which is basically the same as in open-water areas.

The water volume occupied by the pile foundation is only 0.25% of the total volume, and the actual compression of fish activity space is almost negligible.

The spray radius of automated feeders is usually 8 to 12 meters. Through 120-degree fan coverage, more than 95% of the feed can be accurately delivered to the non-shaded area or the light-shadow boundary, ensuring that fish feed in the best light-sensing environment.

In addition, the smart fishery system automatically collects multi-parameter indicators every 10 minutes, and its control accuracy is 40% higher than that of manual management, ensuring that under high-density breeding conditions, the biological carrying capacity of the pond always remains within the 98% safety threshold.