Difference between revisions of "Grid Extension vs Off grid, Island / Isolated System"
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==== ROT (3) ==== | ==== ROT (3) ==== | ||
− | '''Question:''' Is an island / isolated grid a viable option compared to stand-alone / off-grid soutions or grid extension? | + | '''Question:''' Is an island / isolated grid a viable option compared to stand-alone / off-grid soutions or grid extension? |
<div><span>Estimate the total number of connections (N) in a rural community within a 500m radius from the rural community centre.</span></div><div> </div><div><span>If cross section can be increased, up to 600 meter are possible.</span></div><div> </div><div><span>N > 100 => isolated grid could be a viable alternative to grid extension or stand-alone systems. Viability depends on load density.</span></div><div> </div><div><span>N < 100 => technically, an isolated grid could be the least cost solution. It may however be challenging to sustain an adequate level of O&M as well as efficient cash management over time due to the limited size.</span></div><div> </div> | <div><span>Estimate the total number of connections (N) in a rural community within a 500m radius from the rural community centre.</span></div><div> </div><div><span>If cross section can be increased, up to 600 meter are possible.</span></div><div> </div><div><span>N > 100 => isolated grid could be a viable alternative to grid extension or stand-alone systems. Viability depends on load density.</span></div><div> </div><div><span>N < 100 => technically, an isolated grid could be the least cost solution. It may however be challenging to sustain an adequate level of O&M as well as efficient cash management over time due to the limited size.</span></div><div> </div> | ||
==== <span>Model calc for ROT (3)</span> ==== | ==== <span>Model calc for ROT (3)</span> ==== | ||
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=== ROT (4) for grid extension vs off-grid systems === | === ROT (4) for grid extension vs off-grid systems === | ||
+ | ==== <span>ROT (4)</span> ==== | ||
+ | <div> </div><div><span>Estimate the expected load of a rural community (L). Sweco 2009 (Appendix 3) can be used to evaluate the load demand of different users.</span></div><div> </div><div><span>Find the average distance (D) from the rural community to the centralized grid.</span></div><div> </div><div><span>Calculate an approximate installed capacity (P) for the off-grid system by multiplying the load (L) by a factor of 1.5 – 3.0. </span></div><div> </div><div><span>System reliability increases with a higher multiplication factor.</span></div><div><span>Modest energy resources require a higher multiplication factor.</span></div><div> </div><div><span>Case 1 =<span> P < 0.7 x D => An off-grid system is likely to be the most viable option</span></span></div><div> </div><div><span>Case 2 =<span> P > 3 x D => Grid extension is likely to be the most viable option</span></span></div><div> </div><div><span>Cases between P < 0.8 to P > 2.9 or 21 are undefined, individual adaptation required</span></div><div> </div><div><span>As the Rule of Thumb has a very large open, not defined, range it gives no solutions for many cases. </span></div><div> </div> | ||
+ | ==== <span>Model calc for ROT (4)</span> ==== | ||
+ | <div> </div><div><span>P = L x D =<span> 2.5 kW x 2 = 7 </span></span></div><div> </div><div><span>“D” assumed to be 2</span></div><div><span>“L” estimation after using SWECO 2009</span></div><div> </div><div><span>Households: 1,000 x 0.2 kW</span></div><div><span>Institutions: 50 x 0.8 kW</span></div><div><span>Small businesses (e.g. shops): 100 x 0.5 kW</span></div><div><span>Small industrial costumers: 50 x 2.0 kW</span></div><div><span>Total connections: 1,200 = 3.5 kW</span></div><div> </div><div> </div><div><span>Case 2 = P (7) > 3 x D (2)</span></div><div> </div><div> </div><div><span>Grid extension is likely to be the most viable option</span></div> | ||
= Further reading = | = Further reading = | ||
Revision as of 12:30, 20 August 2010
Main decision criteria
- Distance to the national / centralised grid (incl. capacity of grid)
- Demand
- Population density and number of households
- Long-term demand (in kwh and terms of energy services) and peak load (in kw)
- Number and (expected) demand (growth) of productive end uses / industrial users
- Levelized costs of energy production (to be consideres: long term marginal costs) in centralised grid and extension costs.
- Levelized costs of energy production in isolated system
- The selection of socially and environmentally appropriate technologies
- ...
Acknowledgement
Important considarations
Grid vs off-grid vs evolutionary approach
By the time the population has outgrown a particular service delivery level, incomes are likely to have risen and population densities increased, resulting in entirely different economic conditions under which other temporary solutions might now become feasible (such as added PV modules to the battery system at home, or mini grids connecting most village households). A grid-connected city person may find it difficult to imagine, but even the simplest first step up from kerosene lighting, a battery-based modern CFL or LED lamp, would immediately improve the quality of life for rural households. There are numerous options to improve living conditions without having grid electricity, and all have fairly low investment costs. Indeed, a range of individual alternatives should be promoted to improve the quality of rural life across the board and create wealth, to commensurate with households’ desire and ability to pay for such services. Although these services constitute a major step up from prevailing living conditions, several subsequent steps will still be required to reach comparable conditions in the future as in urban areas.
Development of criteria / rules of thumb
Basic definitions
Grid-connected (on-grid) power supply / provision is defined as electricity supply which is fed by centrally generated electricity, and uses a network of (high,) medium and low voltage distribution grid system that exceeds one village. Grid extension is therefore a network expansion from the national power transmission system to new areas and communities. Whereas decentralized power provision is understood as power generation in the village, such as solar home system or a mini-grid powered by a diesel generator / hydro power plant. Grid-connected (on-grid) electrification comprises the connection of entire villages through network extension (grid extension), so the construction of new transmission lines (transmission lines), as well as network densification measures. The latter are divided into two categories: (1) Grid densification by transformation, if villages which are located in close proximity to an existing transmission line will be connected, change of voltage level. (2) Densification within an existing low-voltage distribution grid, connection of additional households.
Decision tree
Cost-effectiveness criteria typically include distance to the existing grid, population size, affordability and productive potential. A consequence of using cost-effectiveness criteria is that they are likely to promote the connection of communities with less poor people. A cost-effectiveness approach can be justified due to its emphasis on financial sustainability.
One example of using cost-effectiveness criteria is how the Pakistan Rural Electrification Project selected communities. They selected communities with I/K ratios > 24, with I being the population size and K the distance to the grid.
Additional examples are:
Rural Electrification in Benin....{Julian Frede / Francois Carme, pls add here}
Rural Electrification in Madagaskar....{Sören David, pls add here}
Rules of thumb (ROT)
The suggested rules of thumb (ROT) for community selection are based on cost-effectiveness criteria. The source of these rules is NORAD 2009, however they have been adapted based on experience during the implementation of Energising Development and discussions with the above mentioned experts.
ROT (1) for grid extension
ROT 1
Question: Is grid extension a viable option?
- Estimate the total number of potential connections (N) in a rural community. Due to time span between planning and execution one may take into consideration the grid extension within the next 2-3 years. The topography is also crucial for this decision. Normally households are the dominating customer group, however normally not all of them connect immediately (micro-finance & diversification of marketing strategies to be considered). Be aware of difference in costumer profiles. Industrial consumers have higher demand and different load profiles.
- Find the average distance (D) from the rural community to the centralized grid<span />
- Calculate the number of connections (N) per distance = N/D
ROT (1) model calculation
village data for model calculation
- Site name: HHPS Hopefully Having Power Soon
- Households: 1,000
- Institutions: 50
- Small Businesses (e.g. shops): 100
- Small industrial users: 50
- Total Connections: 1,200
- Population: 5,000
- Case (1) Distance from the Grid = 100 km
- Case (2) Distance from the Grid = 15 km
- Connections within 600 m radius of the centre = 800
Excercise: Calculate the number of connections (N) per distance = N/D:
ROT (2) for single-phase vs three-phase config.
ROT (2)
Question: If grid extension is a viable option, which configuration?
- Estimate the total number of connections (N) in a rural community.
- Find the average distance (D) from the rural community to the grid
- Multiply the number of connections (N) with the distance = N x D
Model calc for ROT (2)
For longer transmission lines, >5 km, with medium high voltage, 15 kV, 3-phase transformers are most common and practicable and no extra calculation is required.
ROT (3) for isolated grids
ROT (3)
Question: Is an island / isolated grid a viable option compared to stand-alone / off-grid soutions or grid extension?
Model calc for ROT (3)
ROT (4) for grid extension vs off-grid systems
ROT (4)
Model calc for ROT (4)
Further reading
- Best Practice Guide For Planning”, NORPLAN & NORAD, October 2009
- Assessing technology options for rural electrification. Guidelines for project development. Draft report. Sweco, Oslo, 2009
- ...