Water resources are a fundamental material basis for the survival and development of human society. As the global population grows and lifestyles change, the scarcity of freshwater has become an increasingly urgent issue. China, which accounts for 20% of the world's population, has only 6% of the world's water resources, and per capita availability is just one-fourth of the global average. This severe shortage has hindered economic growth and damaged the ecological environment. To address this challenge, seawater desalination has emerged as a critical solution. However, China’s technology in this field still lags behind that of many foreign countries.
**The Gap with Foreign Countries**
1. **Technology**
China lacks deep research on core components such as low-temperature multi-effect systems, materials, and hydropower co-production. Equipment verification and environmental conditions do not meet technological development needs, and there is a lack of engineering practices in designing, manufacturing, installing, commissioning, and maintaining large-scale desalination units. There is an urgent need to develop complete technologies and training teams through scale demonstrations. Key components like reverse osmosis membranes, high-pressure pumps, and energy recovery devices are still mainly imported. The concept of nuclear desalination has been around for years, but no practical applications exist yet. The interface between nuclear reactors and desalination remains at the design stage, requiring further development.
2. **Industrial Scale**
Most Chinese desalination projects are limited to 1,000 tons per day, while foreign countries have reached 100,000 tons. China's desalination output accounts for only 0.3% of the global total, showing a significant gap.
3. **Implementation Mechanism**
There is no centralized agency or industry alliance to coordinate efforts. Desalination requires integrated planning across government guidance, industry coordination, policy support, and innovation. Full coordination among all stakeholders is essential to drive industrial growth.
4. **Demonstration and Investment**
Insufficient state funding for large-scale demonstration projects has limited the progress of technological development and the commercialization of results.
**Solar Water Desalination Technology Development Status**
Cost remains the biggest obstacle in desalination. For a 10,000-ton/day reverse osmosis plant, the cost breakdown includes chemical consumption (0.3–0.5 yuan/ton), power (2.2–2.5 yuan/ton), membrane replacement (0.3–0.5 yuan/ton), labor (0.2 yuan/ton), depreciation (0.9–1.2 yuan/ton), maintenance (0.2–0.4 yuan/ton), and management (less than 0.1 yuan/ton). Total cost is approximately 4.2–5.4 yuan/ton, with power and depreciation being the largest contributors.
To reduce energy use and meet special needs, solar desalination has been developed. It can be divided into direct and indirect methods.
**Direct Method**
This involves using solar collectors to heat seawater directly, producing fresh water through evaporation and condensation. Types include shallow disk, tilt, and multi-effect distillers.
- **Shallow Disk**: A simple system with a black tray and transparent cover. Sunlight heats the water, causing evaporation. Condensed steam collects as fresh water. Daily production is about 2–4 kg/m²·d.
- **Tilt Type**: Improves efficiency by allowing seawater to flow along an incline. Can increase production by 30–60%, but presents technical challenges.
- **Multi-Effect**: Uses waste heat from steam condensation to heat more seawater, increasing efficiency significantly. Daily output is 7.5–10 times higher than the shallow disk method.
**Indirect Method**
This method uses solar energy to generate heat or electricity for desalination. It includes distillation, reverse osmosis, and electrodialysis. While more complex and costly, it offers greater water production capacity and is suitable for medium-scale applications.
**Adsorption Solar Desalination System**
A promising new approach is the adsorption-based system, which uses materials like zeolite and activated carbon to absorb and release water vapor. This system operates by heating the adsorbent during the day and cooling it at night, enabling continuous operation. It has advantages such as high efficiency, low cost, and suitability for remote areas.
**Characteristics and Key Technologies**
Compared to traditional methods, adsorption solar desalination offers high efficiency, low operating costs, and minimal moving parts. It uses solar energy, making it ideal for off-grid locations. However, key challenges remain, including improving thermal conductivity, optimizing heat transfer, and enhancing system integration. Despite these challenges, the technology holds great potential for future development.
Chemical Anchor
Chemical Anchor
Hebei Qianmu Fastener Manufacturing Co., Ltd , https://www.qmjgjfasteners.com