INSTALLATION OF A 6KW MICRO HYDROPOWER PLANT AT THE NEW 12M HIGH FUNZWE EARTH DAM (4)
There are no expenses on energy such as diesel or electricity with this type of project.
This water was later fed into an irrigation channel downstream of the dam. When I first mooted this concept there was initial scepticism within the Technical Service Branch of the Department of Agriculture, not because the technology was new, but simply because it had not been done before within the branch. Had it been responsible for funding, the project would never have seen light of day. Fortunately, I was able to implement this project because I had access to funds through RIF which was funded by the World Bank. I was therefore pleasantly surprised when I visited a dam in 2014, which was being constructed by the Department of Agriculture, where the siphon intake idea was being replicated.
I have, therefore, a dream or a vision that if a small dam can be shown to generate electricity at Funzwe Dam, this technology can be replicated at other small dams in Zambia for rural electrification or for use by farmers. This idea of failing to use existing dams for power generation is not limited to Zambia alone. In the USA an estimated 97% of the country’s 79,000 dams are not generating any power, many having been built to control water levels or for other purposes. Equipping these dams to produce electricity could provide an additional 7,300 MW of capacity by 2025. The environmental impact would be minimal as these dams are already built .
These small dams would help sustain the lives and livelihoods of local communities through multiple uses, by securing access to water:
•for domestic use;
•for agriculture, with the aim of increasing the agriculture yields of smallholder farming;
•for fish farming;
•for livestock; and
•for various water-dependent activities such as mini hydropower systems, brick-making, tree growing, and food processing.
These small dams will also be beneficial instruments for climate change adaptation by attenuating (lessening) the impact of flooding.
There is consensus of opinion that poverty cannot be alleviated without access to modern energy. Energy is so important that it should have qualified to be part of the MDGs so much so that some people referred to it as the missing MDG. However, where there is no consensus at all is how this access to modern energy should be achieved. The age old question of grid extension versus decentralized electrification through renewable energy technologies, RETs, especially through pico and micro hydropower is still there when one looks at the detailed Rural Electrification Master Plan (REMP), which is to serve as a blueprint for rural electrification in Zambia for the period 2008 – 2030 given in the table above: From this table it is clear that rural electrification will be mostly achieved through grid extension despite the commonly held belief that grid extension is very expensive when compared to rural electrification through decentralized electrification using RETs and solar. Pico and micro hydropower does not feature at all and mini-hydro power development is a paltry 0.3% in this Rural Electrification master Plan.
The Rural Electrification Master Plan was prepared by JICA but in Vietnam JICA came up with the “Village Hydro” model concept, which was defined as small water-driven systems suitable for power supply in rural communities not connected to the national grid and were of the view that systems in rural communities and the demand for power rarely justify larger systems.
The technical features of Village Hydro developed in the JICA study include a standardised design based on domestic technologies, locally available equipment and materials, operation and maintenance by local people, and lightweight components that can be carried by hand (such as PVC pipes). Standardisation effort lowers costs and improves the quality of equipment, and facilitates subsequent replication of similar power systems to other sites.
A Village Hydro system serves a relatively small area, because extending the distribution lines beyond the limit, usually less than two km without transformers- is very expensive. Villagers living outside of the service area are expected to use battery-charging units installed at the powerhouse, thereby increasing the number of electrified households while minimising additional investment.
The Japanese also prepared the Zambian REMP. As is evidenced from the above table pico/micro is not the RET of choice of giving electricity to the poor. It is grid extension and PV which are the technologies of choice.
The predominant approach that most governments take to increase electricity access has been central grid extension. Several studies, however, point to the high costs of central grid extension to rural areas that are often sparsely populated. Low population density and a relatively poor consumer base with low electricity consumption act as disincentives for traditional utilities, such as ZESCO, which led to the birth of REA, to provide electricity in rural areas.
Pico hydropower is commonly defined as hydroelectric power generation with a maximum electrical output of five kW (kilowatts). It can be installed on a river/stream (run-of-river scheme) or with a dam but the introduction of a dam increases the cost of the project. A run-ofthe-river scheme does not stop the river flow but instead diverts part of the flow into a channel and pipe, usually referred to as a penstock, and then through the turbine. The disadvantage of this approach is that water is not carried over from the rainy season to the dry season and from a wet year to a dry year. The assessment of the correct hydrology becomes very important which is sometimes hampered by lack of flow data which can result in wrong computation of power generation. It can also be installed at existing small dams of which there are plenty in Zambia, which were meant for other purposes other than hydropower generation. It is cost effective, environmentally friendly and with the possibility that the turbine can be manufactured locally. Lamasat, a local company based in Makeni, Lusaka, produces high quality PVC pipes which can be used for penstocks.
Before the pioneering works of Phillip Maher and Niger Smith on pico hydro, who demonstrated that rural communities do not require large amounts of electricity, rural electrification was largely the preserve of grid extension through large hydro. Small-scale hydropower systems benefit in terms of cost and simplicity, originating from different approaches in the design, planning and installation compared to those which are applied to large hydro. Recent innovations in pico hydro technology have made it an economic source of power even in some of the worlds’ poorest and most inaccessible places. It is also a versatile power source. AC electricity can be produced directly, enabling standard electrical appliances to be used and the electricity can be distributed to a whole village. Common examples of devices, which can be powered by pico hydro are light bulbs, radios, televisions, refrigerators and food processors such as hammer mills.
At the Funzwe Earth Dam, there are two 150mm diameter low level steel outlet pipes already installed. One of the project proposals is to connect a 1 kW pico hydro turbine/generator to each pipe. Total output is, therefore, from 2 pipes is about 2 kW. Each of the two steel pipes will be connected to a short 150mm diameter PVC pipe, not more than 4m long which in turn will be connected to the pico hydro unit. PVC has been chosen because of its smooth bore which results in less friction and therefore more power generated.
Power calculations for a 150mm welded steel pipe 90m long including equivalent pipe lengths due to bends and valves with an effective roughness for welded steel pipe of 0.3 mm under varying flows are shown in the table below. A gross head of 8m has been chosen although it is likely that the head can be improved upon by a metre or so. Power at Turbine = 80% of Flow* net Head *gravity constant i.e. 0.8*Q*hnet*9.8
Power at Generator= 85% of Power at Turbine i.e. 0.85*Power at Turbine It is clear that increasing flows will not result in increased power generation because of the effects of friction. Just multiplying the flow and head without taking into account the friction losses can lead to high power generation figures, which will not be realised in the field. From the chart at a head of 8m with an optimal flow of 35 litres per second, 1.2kW of power can be generated by each of the two machines bringing the total to 2.4kW.
The project cost for a 2 kW pico hydropower scheme is K55, 000.
The original design had one low level outlet steel pipe of 300mm diameter. However, the client gave permission to the contractor to instead use two (2) 150mm diameter steel pipes. These smaller diameter pipes have resulted in high friction losses resulting in a maximum power generation of only about 2.4kW. This will mean that the dam site hydropower potential will be underexploited because of the high friction losses which will result in only producing 2.4kW when the site has the potential to produce at least 6.0 kW. It is therefore recommended that a new 300mm PVC be laid with an intake at about 987m, 3m below the full supply level.
Lessons can be learnt from Kenya where UNIDO constructed pico hydro schemes based on the 1 kW pico hydro units donated by the Chinese government. One scheme had 2x1 kW pico hydro units i.e. 2 kW power output. To make pico hydro more viable it is important to use it for productive uses such as grain milling as well as lighting. It was later found out that the capacity of the donated pico-turbines was insufficient for significant productive uses. Moreover, the 1kW maize mill installed was too weak and technically not appropriate for producing flour.