In order to make full use of the energy recovered by the heat exchange system, Wei Minsheng renovated all the roofs in the urban units.

After the leak-proof compartment was completed, most of the area was made into a 40-centimeter-deep pool, except for the surrounding aisles, and the inner surface of the pool was completely covered with black tiles.

The warmer sea water on the sea surface around the urban unit is pumped to the roof of the building, forming salt ponds.

At the same time, the solid guardrail around each roof has been raised to three meters, and a sloping transparent glass roof is fixed in the space enclosed by the guardrail, forming a relatively closed space inside the entire roof guardrail.

The low side of the glass roof is about two meters long, facing the outside of the urban unit, and the high side is level with the three-meter-high guardrail, towards the center of the urban unit.

This can prevent damage to these glass roofs from storms at sea.

Underneath the glass roof is a heat exchanger and an insulated water tank.

The two ends of the high-pressure heat exchanger are connected to different insulated water tanks, but the temperature of the fresh water in the tank is different.

The refrigeration end is connected to a cold water tank, which is used for the cold water circulation of the water-cooled air conditioner.

The heating end is connected to the insulated water tank where the hot water is stored, and the water temperature in the water tank is raised to more than 80 degrees.

This hot water is used for the daily washing water supply of the residents of the whole building.

Since the use of hot water is consumable, in order to raise everyone's awareness of water conservation, a separately designed smart water meter is installed on the pipes of hot water supply to households.

This kind of smart water meter is different from the domestic smart water meter, because it only has one automatic meter reading function.

The water meter of each household must be connected to a special low-voltage power supply to work, otherwise the water meter is turned off.

The low-voltage wire, in addition to providing power for the switch of the smart water meter, also uses the principle of the power cat to exchange data with the controller of each building.

The controller of each building is directly connected to the network platform, and the controller reads the working status of the water meter through a special pulse signal and feeds it back to the information processing center.

In the case of abnormal water consumption and short-term exceeding the preset value, the controller can also actively turn off the water meter to prevent the waste of fresh water caused by the accidental bursting of the water pipe at home when no one is at home.

A smart water meter has four interfaces, which control the entry and exit of two water supply pipes at the same time.

The price of hot and cold water is the same, and on this island with no rivers and far from the mainland, the price of tap water equivalent to 10 yuan per ton is simply a benefit, attracting the attention of a large number of Tuvaluan citizens.

Due to the high temperature in the hot water tank, there are serious safety risks associated with direct use.

Therefore, the high-temperature water coming out of the hot water tank is also connected to a small corrosion-resistant cooling tower.

The cooling tower is located in the center of the rooftop salt pan, and around its base is a slightly larger square pool.

The bottom of the square pool is connected to the outside salt pan by a small hole, and the sea water in the salt pan can enter the square pool freely.

A small wooden water wheel driven by a small motor from discarded electrical appliances is placed next to the cooling tower, which is the idea of working people from another world.

Because ordinary water pumps are susceptible to corrosion when used for the circulation of salt water, the talents of the other world have come up with such a way that the motor will not come into contact with the corrosive salt water at all, thus prolonging the life of the motor.

The slowly rotating waterwheel pours water from the square pool through the bamboo tube on the waterwheel and dumps it over and over again onto the cooling tower.

The seawater that flows down from the top of the cooling tower, with the heat provided by the cooling tower, evaporates much more than it would be if the water was constantly sprayed with a water pump.

Because the rate at which water evaporates is related to the temperature and the surface area it touches with air, a constant flow of water will only take away a large amount of heat, but the increase in water temperature will be limited.

Through the rhythmic watering method of the waterwheel, the temperature of the seawater passing through the cooling tower can be formed into a large temperature change range from cold to hot.

The high temperature part of this temperature range accelerates the evaporation of water, which is conducive to increasing the evaporation rate of seawater.

As the seawater evaporates, the concentration of seawater in the small pool becomes higher and higher, and when the saturated concentration of salt is reached, crystals are formed and precipitated and deposited at the bottom of the pool.

When these coarse salt crystals reach a certain level, they can be collected and further processed into refined salt, and then sent to another world in exchange for other materials they need.

And this evaporated water, when it comes into contact with the glass roof with a relatively low temperature, will condense into water droplets.

As the water droplets increase, and the sloping glass surface, the tiny droplets merge into a fine stream of water under the force of gravity, which flows down the top of the glass into a water pipe installed below the edge of the glass.

Another function of the sloping glass roof is to collect rainwater while preventing it from diluting the concentration of seawater in the salt ponds below.

The transparent glass roof also allows sunlight to pass through, and the black tiles at the bottom of the salt pond absorb the heat and heat the seawater in the salt pond, increasing the rate of evaporation of the seawater in the salt pond.

All the fresh water collected by the glass roof is collected through sewer pipes and stored in a freshwater pool outside the city.

The hot water, which has been consumed by the cooling tower, is reduced to more than 40 degrees Celsius by passing through the pipes immersed in the salt pond, raising the temperature of the sea water in the salt pond.

Hot water at this temperature can be used for washing with peace of mind when it is combined with a mixing switch.

In the process of heat exchange, the water temperature in the salt pond is also increased as a whole, which accelerates the evaporation rate of seawater and the precipitation of coarse salt crystals in the salt pond.

Although the area of salt ponds on the roofs of each house is not large, the total rooftop area of the entire urban unit also reaches nearly 500,000 square meters.

This kind of salt pond, which is almost not affected by the weather, can produce coarse salt efficiently around the clock under the influence of the recycling and comprehensive utilization of a large amount of domestic waste heat and its closed special structure.

The salt production rate of this salt pond is at least three times that of the traditional salt drying field, and the average daily salt production reaches nearly 40 tons.

With such production, coupled with the time difference between the two worlds, the salt production of this single urban unit alone is enough to meet the daily needs of nearly one million people.

The quality of refined salt produced by modern technology, as well as the relatively low price, how can those otherworldly slag salts have the ability to compete with it.

Before Huaxia Guo issued a sales task, those merchants with keen business vision, driven by high profits, sold these things called snow salt to any place where there was a demand, and at the same time brought all kinds of precious medicinal materials and gold and silver to Huaxia Kingdom.

At the same time, thanks to the thermal insulation under the salt ponds and the almost free water-cooled air conditioning, the temperature changes in those houses on the top floor are no longer directly affected by the sun.

With a comfortable living environment, these houses, which were not rented out before, have gradually been accepted by everyone.