*Diffuse Horizontal Irradiance (DHI) is the amount of radiation received per unit area by a surface (not subject to any shade or shadow) that does not arrive on a direct path from the sun, but has been scattered by molecules and particles in the atmosphere and comes equally from all
*Global Horizontal Irradiance (GHI) is the total amount of shortwave radiation received from above by a surface horizontal to the ground. This value is of particular interest to photovoltaic installations and includes both Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DHI).
*Global Horizontal (GHI) = Direct Normal (DNI) X cos(θ) + Diffuse Horizontal (DHI)

Global Horizontal Irradiance (GHI) is the total solar radiation incident on a horizontal surface. It is the sum of Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance, and ground-reflected radiation.Hoogwijk [3] defines it as the geographic potential reduced by the losses associated with solar-to-electric power conversion. … The technical PV potential is the actual usable solar energy or power once it has been transformed into electricity by PV systems. Jan 1, 2016

PHOTOVOLTAIC POWER POTENTIAL IN SUDAN
Solar Energy With an average sunshine duration of about 9 hours a day, Sudan’s solar energy achievements so far appear to be very poor. Most of the solar technology installations in the country are Photovoltaic (PV) with a total installed capacity of about 2 MW (Rabah, A.A., et al., 2016, p.7). Approximately half of the installed capacity is associated with the telecommunication industry (e.g. remote off-grid antennas and satellites The country, represented by its Ministry of Higher Education and Scientific Research (MHESR), does realize the importance of renewable energy and solar energy in particular in solving essential live problems especially in rural parts of the country.
The technical potential for renewable energy in Sudan, at both a centralized and a distributed level, is very high. The annual average solar radiation exceeds 2000 kWh/m2, which is considered to be among the highest globally. Figure 1 shows the potential for electricity generation from solar PV throughout Sudan as estimated in the World Bank’s Solar Atlas.Distributed generation systems (including off-grid systems) present a big opportunity for scaling access to clean and modern energy services in Sudan (and sub-Saharan Africa) due to their modular nature and economic competitiveness as compared with the grid extension. This point was highlighted in several reports by leading energy organizations such as the International Renewable Energy Agency (IRENA), the International Energy Agency (IEA), and Bloomberg New Energy Finance (BNEF). Furthermore, the drop in costs of renewable energy equipment (such as solar cells, batteries etc), due to economies in scale and advancements in manufacturing, indicates their economic feasibility is improving.

Figure 1 Sudan’s technical potential for solar PV technology (image credits: © 2019 The World Bank, Source: Global Solar Atlas 2.0, Solar resource data: Solargis)
Weather in Khartoum:
January:Hot winter month with average temperature varying between 15.6°C and 30.7°C , the coldest month.
February:The last month of the winter, with average temperature fluctuating between 16.8°C and 32.6°C . March:The first month of the spring,is a very hot month between min 20.3°C and max 36.5°C.
- April : It is a blistering spring month with average temperature 24.1°C and 40.4°C . May:The last month of the spring, is also a scorching month, 27.3°C and 41.9°C . June:The first month of the summer, is also a scorching month, with 27.6°C and an max 41.3°C. July:Is another torrid summer month, with average temperature fluctuating between 26.2°C and 38.5°C . August:The last month of the summer with temperature 25.6°C and 37.6°C . September:The first month of the autumn,still a torrid month,between 26.3°C and 38.7°C . October : The same as September, is another torrid autumn month with 25.9°C and 39.3°C . November :The last month of the autumn, is also a sweltering month, with 21°C and 35.2°C . December :The first month of the winter ,is still a hot month, with average temperature 17°C and 31.7°C.
The month with the most sunshine in Khartoum is February, with an average of 11.1h of sunshine. Months with the least sunshine in Khartoum, Sudan, are July and August, with an average of 9h of sunshine. Months with rainfall in Khartoum are March, May through November. Months with the highest UV index in Khartoum are March through September, with an average UV index of 12. December is the month with the lowest UV index, with an average maximum UV index May is the warmest month in Khartoum, Sudan, with 27.3°C and 41.9°C .The month with the highest average low temperature is June (27.6°C). The coldest month (with the lowest average low temperature) is January (15.6°C). The month with the longest days in Khartoum, Sudan, is June, with an average of 13h of daylight. The month with the shortest days is December, with an average of 11.2h of daylight
Ultraviolet Index:UV Index; The classification of the amount of UV radiation that is expected to reach the surface of the ground when the sun is at the top during the day and which may be harmful to human health, is called ‘UV Index’. 1 UV I = 0.025 W / m2. In Sudan ultraviolet radiation is quite high. The values of the index in this range indicate the highest possible risks of ultraviolet radiation on living things.The time spent in the sun should be limited to very short.
Optimal tilt angles for fixed tilt solar PV panels for Khartoum and Ankara
Country Representative City Nearest Meteorological Station Station Lat. (deg.) StationLon. (deg.) Opt tilt
Sudan Khartoum Gondar, Ethiopia 12.53 37.43 18
Turkey Ankara Ankara 40.12 32.98 29