SPIS Toolbox - Evaluate Geophysical Parameters
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2. Evaluate Geophysical Parameters
Several geophysical parameters can be used to assess SPIS markets. This module highlights 3 that are crucial to the viability of SPIS applications as discussed in Chapter 1: Land cover-land use, solar irradiation and precipitation (under water availability). If the state of these three parameters is unfavourable in the area under assessment, SPIS is unlikely to be practical. An additional 4 parameters that are key to the market assessment for SPIS are also identified – these do not affect the viability of SPIS; they affect the success of SPIS adoption on a case by case basis. The 7 parameters are expounded on below.
Topography
Topography describes the elevation and the relief features on the earth’s surface. Relief features include both natural and man-made landforms such as roads, hills, valleys, railways among others. Key topographical features in evaluating market potential for SPIS are slope and aspect.
Slope is a measure of the change of elevation over a certain distance. It answers the question of how steep an area is and is a determining factor for the type of irrigation system to promote. This in turn determines the cost and labour requirement (e.g. erosion control practice and water conveyance channels). For instance, surface irrigation is more suitable in undulating areas and is cheaper compared to sprinkler and drip irrigation which are more suited on steeper or unevenly sloping land. Therefore, coupling steep lands with a factor like low access to finance (discussed in Chapter 3) would lead to weak market potential for SPIS.
Aspect describes the direction which a slope faces. It is especially relevant for systems located in higher latitudes and rarely affects systems close to or along the equator. Aspect influences the amount of solar radiation that the slope receives as well as the daily range of temperature and the relative humidity on the slope.
Generally, more direct sunlight tends to fall on the south and southwest slopes while North aspects of slopes are more shaded in the northern hemisphere. The converse is true in the southern hemisphere where more direct sunlight tends to fall on the north and northwest slopes.
Topographic analysis for potential SPIS sites can be determined through use of topographic maps that depict the physical configuration of the earth’s surface using contour lines as wells as symbols for man-made and natural features. Users can also use Digital Elevation Models (DEMs) that are specialized databases that represent the relief of a surface between points of known elevation. DEMs can be used on Geographical Information System (GIS) platforms. This should be followed by a ground-truthing exercise to determine the exact slope and aspect of the area of interest.
Outcome/Product
- Determination of slope and aspect of potential SPIS markets
- Selection of suitable irrigation systems based on the topography of the potential SPIS market
Data Requirement
- Topographic Maps
- Digital Elevation Models(DEMs)
People/Stakeholder
- Lands and Survey Authorities
Important Issues
- Care must be taken when designing irrigation systems on steep slopes as such areas are prone to erosion and runoff.
Crops and Livestock
An overview of the prevailing types of crops and/or livestock in the country or region of interest serves to understand which SPIS are most suitable and is also indicative of the market potential for SPIS technology. This is particularly relevant for SPIS system suppliers and entities seeking to promote adoption of SPIS by farmers. This information can be sourced from government ministries in charge of agriculture, global research studies on cultivated areas, FAO databases on crop cultivation among others.
Additionally, stakeholders interested in promoting or setting up SPIS schemes can use agro-ecological zones (AEZs) to determine the most suitable crops to be cultivated and animals to be reared in an area. AEZs define areas based on combinations of soil, landform and climatic characteristics and match suitable crops and animals to regions. The zones can also be used to determine the potential yields of the main crops grown within the zone thus helping with income projections of the target market. As discussed under Finance in Chapter 3, access to finance is a key parameter in evaluating a market’s potential for SPIS.
The Global Agro-ecological Zones (GAEZ) portal by FAO and the International Institute for Applied Systems Analysis (IIASA) provide a comprehensive online portal with details on land resources, agro-climatic resources, suitability and potential yield, actual yield and production and yield and production gaps. Stakeholders interested in SPIS can refer to this or similar tools to determine important characteristics that influence the type of crops or livestock in an area.
Outcome/Product
- List of crops grown and animals reared in selected countries or regions
- AEZ classification for selected areas
- Potential crop/livestock yield within the area of interest
Data Requirement
- Global AEZ by FAO and the International Institute for Applied Systems Analysis
People/Stakeholders
- Ministry of Agriculture
Ambient Temprature
As the name suggests, this parameter looks at the temperature of the areas surroundings. This has two main effects on SPIS potential:
- affects the efficiency of SPIS and
- affects the crops and livestock found in an area.
On efficiency of SPIS, temperature is a key factor in the design of pumping systems as it affects the functionality and life span of solar PV equipment. The flow of electricity and the voltage output of solar panels depend linearly on the operating temperature of the panels. Lower temperatures produce reduced resistance to electricity flow resulting in higher voltage outputs; higher temperatures increase resistance and subsequently lead to lower voltage outputs. High ambient temperatures also affect the performance of the system’s inverter by reducing its frequency which in turn reduces its efficiency and the flow rate of the pump.
Due to the variability of climate in different regions, most panels do not operate under ideal temperature conditions. To correct this, panels in hotter regions of the world are often designed with cooling systems to keep the panels within certain temperatures. Additionally, PV systems in different temperature environments must be sized to ensure that the output voltage is not too high, which could damage the equipment.
The range of crops and livestock that are suitable in an area is often affected by ambient air temperature. Analysis of thermal regimes using agro-ecological zoning discussed in the previous section can reveal crops and livestock suited to a region based on its temperature. This may then inform the need for SPIS for the said region.
Outcome/Product
- Determination of ambient temperatures in potential SPIS markets
- Selection of suitable solar technology based on temperature regimes
- Determination of suitable crops and livestock based on temperatures
Data Requirement
- Global AEZ by FAO and the International Institute for Applied Systems Analysis
People/Stakeholders
- Meteorological service providers
Important Issues
- Panel selection should be done with ambient air temperature in mind to maximize efficiency of the system and to ensure adequate voltage output.
Demographics
An understanding of demographic characteristics including population density, age, migration levels and patterns and household income provide additional information when making decisions on potential SPIS markets. These characteristics can be used as proxy indicators of poverty levels, labour availability, prevailing agricultural practices, urban settlements among others.
This parameter cannot be used standalone, but in combination with other parameters can assist in a deeper understanding of social dynamics and cultural conditions for a target region. For example, as earlier mentioned, coupling topography with poverty levels could help infer market potential. Also, analysis of population density and land cover-land use data could highlight densely populated areas or urban settlements which could be a factor in determining the viability of a potential SPIS market. SPIS sites cannot be in densely populated urban settlements however they could be located close to such areas as they provide market for produce.
Evaluating demographic characteristics such as household income alongside business parameters such as financing and incidences of poverty can serve to highlight the capability of households to take up SPIS systems.
Outcome/Product
- Correlation of demographic characteristics with SPIS geophysical and business parameters to identify relevant issues in determining potential SPIS markets
Data Requirement
- Census Reports
- Satellite imagery on global population
People/Stakeholders
- Government Ministries including Ministries of labour and migration
- Statisticians
