可再生海水淡化：岛屿的技术选择（英文版）_79页-19mb

Summary of Renewable Desalination: Technology Options for Islands

Core Content

This document, published by IRENA in 2015, explores the potential of renewable energy technologies for desalination on islands, particularly Small Island Developing States (SIDS). It outlines the technological and economic feasibility of using solar, wind, and other renewable sources to power desalination systems, which are critical for addressing water scarcity on islands due to limited natural water resources and the impacts of climate change.

Main Viewpoints

1. Water Scarcity and Climate Challenges

• Islands often face water scarcity due to limited surface water and groundwater resources.
• Climate change is expected to increase drought frequency, flood intensity, and sea-level rise, worsening water availability.
• Many islands are vulnerable to saltwater intrusion, especially those with low elevation and overexploited groundwater resources.
• Islands in tropical latitudes experience seasonal rainfall patterns, while those in semi-arid climates (e.g., Mediterranean and Atlantic islands) face more variable water supply.

2. Desalination Technologies and Their Suitability

• Thermally driven technologies include Multi-Stage Flash (MSF), Multi-Effect Distillation (MED), and Mechanical Vapour Compression (MVC). These are typically used with fossil fuels but can be powered by renewable energy, especially concentrated solar power (CSP).
• Electric technologies include Reverse Osmosis (RO) and Electrodialysis (ED). RO is the most widely used and efficient for seawater desalination, while ED is suitable for low-salinity brackish water.
• Unconventional technologies such as Humidification/Dehumidification (HDH), Solar Still, and Membrane Distillation (MD) are also discussed, though they are less common and often used for small-scale or off-grid applications.

3. Renewable Energy as a Cost-Effective Alternative

• Renewable energy desalination can be cost-competitive with fossil-fuel-based systems, especially in islands with high import costs.
• The cost of water from RO systems powered by photovoltaics (PV) or CSP can be significantly lower than from fossil-fuel systems.
• Wind-powered RO systems are also viable, particularly for smaller capacities.
• The use of renewable energy reduces dependence on imported fossil fuels and lowers overall energy costs.

4. Technology Readiness and Scalability

• Small-scale desalination systems (10–100 m³/day) are more suitable for islands with limited infrastructure and distributed settlements.
• Medium-scale systems (up to 1,000 m³/day) are appropriate for centralized urban areas.
• Multi-Effect Distillation (MED) is considered the most promising thermally driven technology for coupling with CSP.
• Reverse Osmosis (RO) is the most promising electrically driven technology for coupling with PV or wind power.

5. Economic Assessment

• The Levelised Cost of Water (LWC) is used to compare the economic viability of different desalination technologies.
• PV-RO systems with 7-hour operation are more cost-effective than 24-hour systems due to reduced battery requirements.
• CSP-RO and CSP-MED systems show competitive cost structures when integrated with appropriate storage and infrastructure.
• Wind-RO systems are viable for smaller islands with moderate wind resources.

6. Barriers and Drivers

• Challenges include high initial costs, technical limitations, and the need for reliable renewable energy sources.
• Drivers include reduced fossil fuel dependency, environmental benefits, and the potential for long-term cost savings.
• Capacity building and the establishment of technical service networks are crucial for successful deployment.
• Investor-friendly business models and local infrastructure are necessary to support renewable desalination projects.

Key Information

• Desalination demand varies across islands, influenced by population, tourism, and industrial needs.
• Water withdrawal is a more objective measure of desalination need than water demand.
• Cost of water from fossil-fuel systems can range from 1.6–3.3 USD/m³ for RO and 4.8–9.2 USD/m³ for MED, depending on fuel costs and heat utilization.
• Renewable desalination can significantly reduce these costs, especially when integrated with solar and wind energy.
• Technology readiness is assessed based on existing literature and field experience, with a focus on small and medium-scale systems.
• Best practices include detailed local analysis, understanding of meteorological and hydrological conditions, and alignment with local energy and water policies.

Technology Selection Guide

• The selection of desalination technology depends on:
  • Island size and settlement pattern.
  • Water quality and salinity of the source.
  • Availability of renewable resources (solar, wind, etc.).
  • Local energy and water cost structures.
  • Infrastructure and grid availability.

Conclusion

Renewable desalination technologies offer a viable and sustainable alternative to fossil-fuel-based systems on islands. With appropriate resource assessment and system design, these technologies can provide cost-effective and environmentally friendly water supply solutions. The document emphasizes the importance of tailored approaches, local conditions, and collaboration between governments, research institutions, and private companies to support the deployment of renewable desalination systems.