Power generation with rainwater in residential areas located near by mountains

Abstract. With the purpose of taking full advantage of rainwater, the concept “power generation with rainwater in communities close to mountains” is proposed. A rainwater generating system is designed. According to an application of this system, using the water in diversion canal to generate power supplied for this very community, what changes the community’s electricity power from completely rely on outside supply into partial self-sufficiency. The whole power generation process is not only conforming to sustainable development, but responding to the concept of “green water conservancy”. The design philosophy suggested in this paper could provide a new planning pattern for the construction of residential districts located close to mountains in the future.

Key words: Residential areas；Power generation；Rainwater Green hydropower；Resource utilization

1. Introduction

Rainwater has been utilized for about a thousand years. In Germany [1], it is mainly used in rainwater harvesting and utilization systems, roof garden rainwater utilization system, intercepting pollution and infiltration systems, ecological community rainwater utilization systems, etc. The rainwater using technology of Germany has reached world leading level. Rainwater is often used for improving natural water infiltration capacity in America, such as underground reinjection system and surface reinjection system; in Denmark, the collected rainwater is often used in flushing toilets and washing clothes after filtered; in Australia, the collected rainwater is taken as industry water directly after triple filter processing [2]. The Chinese early utilization of rainwater mostly in arid rural areas, now some cities also start trying to make use of rainwater in city clean, green, road spray, fire control and maintenance of urban water landscape [3,4]. With the development of micro hydro power technology [5,6], rainwater can also be sued for power generation.

The humid subtropical monsoon climate of Chongqing brings abundant rainfall with 1000~1400mm annually. The rainfall data from 1976 to 1980 in Table1 is collected by Cuntan hydrometric station which is on Yangtze River shows that during the rainy season which is from May to September, rainstorm happens frequently and the rainfall is heavy, result in runoff yield particularly quick and large, while it is relatively small in winter. In Chongqing plenty of residential districts are built close to the mountains, with a diversion canal for discharging the catchment in this region. Water is usually large as it rains, as shown in Fig. 1. However, since this part water is influenced by seasons and generally not too large to get people’s attention. In fact, take a residential area in Xuefu road, Nan’an district of Chongqing city for an example, the catchment area is about 1.5km2, annual average rainfall is about 1050mm, every year there’s a considerable number of water flow out. As the situation of lack water and electricity is getting more and more serious, to develop the value of rainwater fully, this paper puts forward "Power generation with rainwater in residential areas located close to mountains", to achieve self-sufficient part of the power in residential areas

2. Principle and practical value

2.1 Basic principle

"Power generation with rainwater in residential areas located close to mountains" is mainly for the residential areas in urban, so the power generation is micro hydro power, the principle of which is the same as large hydro power that is the generator is driven by water turbine to produce electricity. Power can be calculated according to hydraulic head and flow.

2.2 Practical value

On the one hand, compared with the traditional residential areas located close to mountains, the proposed rainwater power generation system is to install a certain number of low-head turbines at appropriate sites to generate electricity with water in canal for the residential use directly, so that the electricity consumption of this community could be changed from completely rely on the power supply into partial self-sufficiency. The whole generation process is green. This system both take full advantage of rainwater and embody the concept of green water conservancy. The design philosophy proposed in this paper could provide a new planning pattern for the construction of communities close to mountains in the future.

On the other side, this system with simple and practical technology is easy to construct and maintenance and quite suitable for popularization. Further more it can be used in relieving the current power supply tension, to a certain extent. The cost in the whole design scheme is low which mainly includes hydroelectric generating set, battery, and electric wire, etc. While the power generated by this system can obtain substantial value, which result in a quite fast capital recovery. As a consequence, the promotion of this power generation will accompany considerable economic value.

3. Project case

The case of a residential area in Xuefu road, Nan’an district in Chongqing has been studied, relevant parameters of this residential area as shown in Table 2.

3.1 Flow calculation

The runoff producing is calculated by UBC WATERSHED MODEL, which is a software used commonly in hydraulic engineering to get runoff of outlet section in some basin caused by rainfall, etc. The results can be obtained by inputting rainfall data (Fig. 1) and parameters (Table 2) into the software and run it, as shown in Table 3

Table3. The results

The comparison curves among 1976 to 1980 as shown in Fig. 2

The above curves indicate that the runoff is greater than or equal to 0.02m3 during most of the year.

3.2 Generating equipment

In consideration of the current and the actual flow in this residential district, the design chooses 600w volute axial flow turbine generator with low head and low flow. This kind of turbine generator demands the hydraulic head is between 0.8m and 10.0 m generally, the flow between 0.017m3/s to 1.66m3/s, which is very suitable for this design. Since it is small power generation, single-phase generator is adequate.

3.3 Installation and working principle

First of all, plan a proper site to install the equipments. The inflow system consist of a intake channel, a water lock, and slide plate to ward off garbage, made of concrete and stone, plank or iron plate, wire netting, respectively. A spiral water intake should be made to get vortex flow to drive the vane wheel rotating. A trumpet type draft tube is needed to make the inside water produce suction which draws the wheel downward and then a powerful motivation is formed to drive the generator working. As shown in Fig3.

3.4 Power generation

Based on the above calculation, runoff is greater than or equal to 0.02m3 during most of the year. Considering the physical condition as geography, drainage channel, etc. in the residential area, we finally determined to install seven electric generators; the generating capacity of each is 600w. So the total power generated in a year is:

3.5 Storage battery

As generators working day and night, and the generated power is not used immediately after it’s produced, besides, there is a remarkable seasonal change in flow, which could cause a disproportion in generating capacity, that is , the power is small during a period of time , while it’s quite opposite during another period of time. So, storage battery is used to store spare power so that it can be utilized in some time. After overall consideration, three fixed type of batteries are used in this design.

4. Conclusions

Firstly, the concept of “power generation with rainwater in residential areas located close to mountains” is put forward, according to which, a generating system with rainwater is designed. With this system, the rainwater can be used for power generation and supply, which makes the residential area could self-supporting partial electric power. It’s obviously that the system proposed in this paper will be beneficial to improve the present situation of lack hydroelectric resource. Especially under emergency conditions such as power failure, natural hazards, etc, this system will play a huge role.

Secondly, this project is simple and practicable at low cost, while the economic value of the generated power is apparently significant, additionally, the cost can be recovered in a short time., What’s more, there is an elementary residue disposing during the process of power generation in this project, without any environmentally harmful outcome, the whole process is accord with “green water conservancy”. Consequently, the concept of “power generation with rainwater in residential areas located close to mountains” has extraordinary promotional value, no matter from economic standpoint or environment protection perspective.

References

[1] J. Q. Li, W. Che. Investigation and analysis on rainwater utilization technology of Germany. Urban environment & urban ecology, 2002, 1 (9): 47- 49.

[2] Y. M. Wang. Research on urban rainwater utilization both domestic and overseas. Journal of Anhui agriculture science, 2007, 35(8): 2384-2385.

[3] J. Q. Li, W. Che. Urban rainwater utilization and water conversation. City and town water supply, 2001, (2): 39 - 41.

[4] W. Luan, D. S. Tang. Research on the comprehensive utilization of urban rainwater resources. Zhi Huai, 2005, (1):78-80.

[5] K Lin, Y Zhao, W. G. Zheng. The application of the technology about electricity generation with rainwater. Power supply technologies and applications, 2013, 16(1.2).

[6] Y .CH. Song, Y. D. Ning, Liu Yu. Small hydropower technology (Science Press, China, 2009)