The Group of Bin Ye from the School of Environment Science and technology published important research paper in the field of the water-energy nexus.

2020-10-09

Recently, Visiting assistant professor YE Bin from the School of Environmental Science and Engineering, Southern University of Science and Technology, published the research paper " Feasibility of coupling PV System with long-distance Water Transfer: A case study of China's "South-to-North Water" on an important journal of resource Recycling – Resources, Conservation & Recycling (IF 8.086): putting forward a new model to make use of limited land resources to develop and make use of renewable energy, and reduce carbon emissions in inland areas.

To nationally optimize limited water resources, the Chinese government has had to build several nationwide long-distance water transfer channels. These channels have placed tremendous pressures on land resources, and some require large quantities of electrical energy to lift the water to a higher altitude. Within the context of the decrease of the cost of solar power generation, this study attempts to make full use of local solar energy resource and upper space of water channel to construct an on-channel photovoltaic (PV) system

Fig. 1. SNWT project routes on map.

This study first determine the installation area of solar panels.

Based on Google Earth image data, the longitude and latitude of critical points on the middle route of south-to-North water Diversion Project were determined.

Since the width of the river is between 9 and 40 meters and the greening width of both sides of the river is 100 to 200 meters, although the average width of photovoltaic modules laid on the river is determined, two schemes are proposed in this study:

Scheme 1: Solar panels just cover the channel water surface area and the average width of the installation area is 40 m as demonstrated in Fig. 2. This scenario has limited impact on the ecological system of the channel and nearby environment.

Fig. 3. Scenario 1 (40 m width).

Scheme 2: The SNWT requires a 100 m greenbelt along each side of the channel, such that the total width of the channel is between 409 and 440 m. Therefore, if 1/2 of the area is covered by solar panels, the influence to the ecological environment of the channel can be controlled to some extent. Based on this argument, the assumption of scenario 2 is as follows: the solar panels are supported 10–20 m above the water surface via pillars and the average width of the rooftop is assumed to be 200 m, covering both the channel and offering slope protection. This scenario is demonstrated in Fig. 3.

Fig. 4. Scenario 2 (200 m width).

The results of this study show that the cost of produced energy for the two cities are 0.36 Yuan/kWh and 0.35 Yuan/kWh respectively, considering both initial investment and operating costs. Comparatively, the desulfurized coal fired power plant baseline prices of the two provinces are 0.3779 Yuan/kWh and 0.3720 Yuan/kWh respectively. Therefore, the feed-in price of solar electricity is lower than the desulfurized coal fired baseline price.

According to the financial parameters setting, without subsidy, the payback period of this project is 19.8 years; however, if the renewable energy subsidy for PV is considered, the payback time can be dramatically reduced to 11.2 years. For return on investment (ROI), the two scenarios are both 4.6% without subsidy, which means the influence of project location is not significant. The reason for this weak influence may be that the initial investments are almost the same for the two scenarios, while the energy output has very limited disparity. Although ROI is only 4.6%, it is very close to the Chinese long-term treasury bond yield in September 2020. This result demonstrates that the rooftop solar projects are on the edge of the break-even line even without any government subsidy.

Alternatively, the evapotranspiration analysis shows that the shadow effects of the solar panels can reduce channel water evaporation to a certain degree. Furthermore, the carbon balance analysis shows the carbon reduction rate of the solar energy can be 98.45% comparing to current coal dominated power system in the project installation provinces. However, some possible questions require further consideration regarding, for example, possible pollution to the channel water flow resulting from the solar panels’ installation and possible damage to the channel water ecosystem.

During the 75th anniversary summit of the United Nations, General Secretary Xi solemnly announced to the world that China would reach carbon peak by 2030 and achieve carbon neutrality by 2060. Replacing high-carbon coal power with renewable energy represented by photovoltaic power generation and wind power generation is one of the key ways to achieve the goals above. The research above provides a new way of thinking for developing renewable energy in inland areas where land resources are scarce.

 

The first author of this paper is YE Bin, visiting assistant Professor, School of Environmental Science and Engineering, South University of Science and Technology, JIANG Jingjing, associate professor, Harbin Institute of Technology (Shenzhen), and LIU Junguo, Professor, School of Environmental Science and Engineering, South University of Science and Technology, are the corresponding authors of this paper.

South University of Science and Technology as the first author unit.

 

This work appreciates the support of the National Natural Science Foundation of China (Grants No.71803074), Natural Science Foundation of Shenzhen City (Grant No. JCYJ20190809162809440 and JCYJ20190806144415100), and the High-level Special Funding of the Southern University of Science and Technology (Grant No. G02296302,G02296402).