Proceedings, 8th African Rift Geothermal Conference
Nairobi, Kenya: 2 – 8 November 2020
Direct uses of geothermal energy - A case of Chinyunyu
hot springs
Musenge Chomba
ZESCO Limited, Stand No. 6949, Great East Road, P.O Box 33304,
Lusaka, Zambia
MChomba@zesco.co.zm;lubutomalumbo@gmail.com
Keywords
Chinyunyu, Direct use, ZESCO, Tourism, Mixed use
ABSTRACT
Chinyunyu hot springs is located in Chinyunyu area of Chongwe District in the Eastern
Province of Zambia, about 100 km east of Lusaka city along the Great East Road. The hot
springs are located about 2 km from Chinyunyu trading centre and about 50 m north of the
Great East Road. The springs discharge hot water at maximum temperature of 64.50C through
the highly foliated metavolcanics. The estimated flow from the well is about 60 litres/min.
According the findings of the recent studies conducted by KENGEN in 2007, Chinyunyu
field is a low temperature geothermal resource associated with fault systems and adjacent to
rock formational boundary. Conceptual modelling indicates that the reservoir temperature is
about 1260 C at a depth of about 500 m. The study recommended drilling of three wells to the
NE of the hot springs to a depth of approximately 500 m to confirm the nature of the
reservoir. Results of simulation studies indicate that more than 2 MWe can be generated from
the geothermal resource by use of binary technology. The study further recommended
consideration of direct use applications such as: balneology, drying, fish farming, irrigation,
tourism. In line with direct use applications, Chinyunyu site can house hotels, green farms,
medical resorts (health facilities), conference facilities, office space, and shopping malls for
revenue. From the current conceptual model and geothermometry, Chinyunyu can generate
power to supply all these auxiliaries without tapping power from the national grid. The
proximity of the site to the central business town (capital city) makes it even more attractive
as a mini-power generation and as a business centre.
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1. Introduction
Chinyunyu hot springs is located in Chinyunyu area of Rufunsa District, Eastern Province of
Zambia and about 100 km east of Lusaka city along the Great East Road. The hot springs are
located about 2km from Chinyunyu trading centre and about 50 m north of the Great East
Road. The springs issue from a localized area adjacent to a swampland. The population in
Rufunsa is over 51,000 (Central Statistical Office Zambia web).
The motivation for this case study originates from The Peppermill Casino & Hotel, the hotel
having hosted the GRC Annual Meeting and GEA Trade Show for several years, which is a
role model for geothermal utilization. Located in Reno, Nevada which has the same
geoscientific parameters like Zambia, the hotel not only derives parts of its electricity from
geothermal plants in the neighborhood of the city, but also generates heat for space heating
from a geothermal well on the property. In 2009 it even briefly generated power from the
geothermal well with a low-heat power generation unit by Pratt & Whitney.
1.1.General objective
The overall objective of this paper is to explore possible utilization of the heat energy from
the hot spring besides electricity generation. Currently, the hot water of about 60°C is just
gushing out from the ground and flowing away forming a stream and not much is been tapped
apart from the local community utilizing it for bathing and other cultural beliefs.
1.2.Specific Objectives
1. To explore direct uses of geothermal energy beside electricity generation
2. To assess investment versus economical and revenue benefits of utilizing heat from
hot springs
3. To carry out geochemical analysis for all samples collected
4. To recommend next line of action on the latest geoscientific surveys that were
undertaken at Chinyunyu hot springs
1.3.Scope of the Assignment
The general scope of the studies seeks to address the objectives outlined above as follows;
1. To explore direct uses of geothermal energy beside electricity generation in the area
as a business case
2. To primarily assess investment versus economical and revenue benefits of utilizing
heat from hot springs
3. Based on the recommendations from the latest geoscientific surveys define propose
the roadmap for direct use exploration studies.
2. Literature review
The earliest reported studies that mentioned the occurrence of the hot springs were those of
Reeve (1963) and Simpson (1967) in which the geological and structural attributes of the
wider Chinyunyu area were discussed. Simpson (1967) reported the occurrence of both the
Chinyunyu and Mwapula hot springs within the vicinity of the Mwapula Cainozoic rift
(Figure 3). The studies identified structural controls in the occurrences of the hot springs
where both the Chinyunyu and Mwapula hot springs occur along the rift boundary faults.
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Simpson (1967) further noted the sulphurous nature of both springs. Reeve (1963) sampled
the Chinyunyu hot spring and noted that whereas the spring is low in total dissolved solids
(TDS); chloride and bicarbonate values are fairly elevated. More studies geared toward
investigating the geothermal potential of the Chinyunyu hot springs were undertaken by DAL
(1986, 1987) as collaboration between the governments of Italy and Zambia of which results
are contained in their progress reports of 1986 and 1987. DAL (1986) investigated and
ranked the various geothermal areas in terms of their potential. DAL (1986) measured 600 C
for the fluid discharge temperature and determined possible reservoir temperatures, based on
solute geothermometry, of 95-1400 C. They concluded that the reservoir could be at higher
temperatures. However, Chinyunyu prospect was not prioritized for exploratory drilling.
Other studies on Chinyunyu include surveys carried out by the Japanese International
Corporation Agency (JICA) in conjunction with the Geological Survey Department in the
Ministry of Mines, Energy and Water Development also could not progress beyond the
planning stage due to lack of funds. The scope of the project was to consider the development
of a health resort and the possible construction of a geothermal power plant to produce
electricity to the local community.
The latest study was undertaken by KNEGEN in 2007 to assess the potential of producing
power at Chinyunyu. Geology, geochemistry and geophysics were conducted and results
analyzed with recommendations for next activities. It is from this background that Zambia
intends to explore the recommendations.
3.0. Materials/Methodology
Preliminary geological, geochemical and geophysical surveys were conducted at Chinyunyu
hot springs between 2007 and 2208. These surveys were done in order to assess the potential
of producing power at Chinyunyu hot spring.
4.0 Data presentation, analysis and interpretation
Geothermal energy use can be divided into three categories: direct-use applications, geothermal
heat pumps (GHPs), and electric power generation. Chinyunyu site is been proposed to turned into
tourist attraction scene in the form of a business centre with a five star hotel couple, conference
facilities, a hospital and small power plant to supply the facilities. Some of the other uses will be in
the aquaculture and laundry for the hotel and the surrounding facilities. The hotel will have a spa for
the customers and visitors. It is proposed to have office facilities to let and small to medium one stop
shopping mall since it is just along the busy great east road connecting the capital Lusaka to the
eastern part of the country.
4.1. Direct use
Probably the most widely used set of applications involves the direct use of
heated water from the ground without the need for any specialized equipment. All direct-use
applications make use of low-temperature geothermal resources, which range between about
50 and 150 °C (122 and 302 °F). Such low-temperature geothermal water and steam have
been used to warm single buildings, as well as whole districts where numerous buildings are
heated from a central supply source. In addition, many swimming pools, balneological
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(therapeutic) facilities at spas, greenhouses, and aquaculture ponds around the world have
been heated with geothermal resources. Other direct uses of geothermal energy include
cooking, industrial applications (such as drying fruit, vegetables, and timber),
milk pasteurization, and large-scale snow melting. For many of those activities, hot water is
often used directly in the heating system, or it may be used in conjunction with a heat
exchanger, which transfers heat when there are problematic minerals and gases such
as hydrogen sulfide mixed in with the fluid.
4.2. Geothermal heat pumps
Geothermal heat pumps (GHPs) take advantage of the relatively stable moderate temperature
conditions that occur within the first 300 metres (1,000 feet) of the surface to heat buildings in
the winter and cool them in the summer. In that part of the lithosphere, rocks
and groundwater occur at temperatures between 5 and 30 °C (41 and 86 °F). At shallower
depths, where most GHPs are found, such as within 6 metres (about 20 feet) of Earth’s surface,
the temperature of the ground maintains a near-constant temperature of 10 to 16 °C (50 to 60
°F). Consequently, that heat can be used to help warm buildings during the colder months of
the year when the air temperature falls below that of the ground. Similarly, during the warmer
months of the year, warm air can be drawn from a building and circulated underground, where
it loses much of its heat and is returned.
Figure 1: Hypothetical Residential Heat Pump System
4.3 Resource Potential for Chinyunyu
The high potential area in Chinyunyu measures between 0.5 and 1 km2 and are controlled by
rift faults. There is a high chance (> 60%) of getting more than 2 MWe using binary system
of generation at both prospects as currently installed at Kapisya (Figures 2 & 3). The
estimates are based on volumetric stored heat model (Monte Carlo simulation) which
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assumed a reservoir temperature range of 120-130oC, resource area of 0.5 - 1 km2, reservoir
thickness of 100 – 500 m, porosity of 3-6% and heat exchanger outlet temperature of
70oC.This is the best model that can be employed for now for these areas due to limited deep
drilling data. Monte Carlo simulation is widely used for geothermal resource estimation and
has also been done for Olkaria I field in Kenya with some realistic estimates (Ofwona, 2005).
Figure 2: Frequency distribution of power potential.
Figure 3: Cumulative frequency distribution of power potential.
The envisaged power that can be produced from Chinyunyu >2MW is sufficient to supply the
auxiliaries which include the mixed use infrastructure and the local community and the rest to
can be sent I to the national grid.
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5.0. Discussion, conclusions & recommendations
5.1 Direct uses
Following preliminary results from the KNEGEN report, there is need to conduct a full
feasibility study for direct uses of geothermal heat energy which should include a full
Environmental and Social Impact Assessment.
5.2. Power Potential
Chinyunyu field is a low temperature geothermal resource associated with fault systems and
adjacent to rock formational boundary. Conceptual modelling indicates that the reservoir
temperature is about 1260 C at a depth of about 500 m. It is recommended that three wells are
drilled to the NE of the hot springs to about 500 m depth to confirm the nature of the
reservoir. Results of simulation studies indicate that more than 2 MWe can be generated from
the resource by use of binary technology (KENGEN, 2007 ZESCO Report).
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deGroot Hedlin C. and Constable H. “Occam’s Inversion to generate smooth two-dimensional
models from magnetotelluric data”, Geophysics, 55, 1613, 1624, 1990
Elder J. W., “Physical Processes in Geothermal Areas-Terrestrial Heat Flow”, Geophy.
Monogr. No.8 Amer. Geophys. Union pp.210-238, 1965
Evans R.L., “Conductivity of Earth materials”-The Magnetotelluric method, Theory and
Practice, Cambridge, 2012
Hjalmar E., Knutur A., Olafur G., “Resistivity Methods in Geothermal Prospecting in Iceland”,
Surveys in Geophysics, Vol. 15, Issue 2, pp. 263-275, 1994
Legg C.A., Senior Geologist, “A Reconnaissance Survey of the hot and mineralized springs of
Zambia, Economical Report of the Geological Survey No. 50, Ministry of Mines and
Industry, Zambia, 1974
Gibson et. al., 2015; Spichak et. al., 2009
Dal, in.tesa. Spa (1987)