Designing a range of technically feasible systems
This stage follows Data Collection and is followed by Sustainability Analysis.
Following the collection of relevant data, a range of technically viable electrical and thermal systems to meet the community development goals can now be designed. This can be done via calculations and with supply & demand matching software such as HOMER. It should be noted that a range of electrical and thermal systems are produced at this stage, selection of the optimal system occurs in the next stage, Sustainability Analysis.
This stage of the methodology is split into:
Electrical system design looks to meet the demand of electrical appliances (including lighting), whereas thermal demand meets cooking and heating needs. For each component, demand profiles must be created in order to match with the supply data collected in stage 2.
This step is intended to produce a range of technically viable electrical systems based upon the results from the Data Collection and Project Definition stages. Electrical demand is first quantified per household as per the development goals. This demand is then matched with the technologies being considered and their relevant data. A range of technically viable systems are produced from this stage, from which the optimal system is selected in the final stage Sustainability Analysis.
Matching software, such as Homer or Merit, is recommended for this task. Below, the strategy, considerations, and challenges associated with this step are explored.
Electrical System Design Strategy
Electrical Demand Profile Design Strategy
To estimate demand profile the following strategy can be employed. It is assumed that lighting is a requirement. This should be performed in conjunction with the below considerations:
Considerations
Annual demand: The population of the village may vary throughout the year (which may be a result of changing seasons or related to seasonal industry or other). This should be established in the "Project Definition" step.
Knowledge barriers: Community members may not be aware of the potential of electricity (for example, LED lighting over kerosene in terms of indoor air quality and fuel costs) hence workshops may be required. This blurs the line between community needs and externally imposed needs from a Western perspective. This should be addressed in "1. Project Definition".
Demand prediction: Demand prediction is extremely difficult as people tend to adjust their consumption according to their comfort and perceptions of a resource. This may be addressed by staggering the development of the electrical energy system and increasing capacity once the community sees firsthand the benefits it may bring. This should be considered as part of the implementation plan in "4. Sustainability Analysis". This may also be addressed by considering Sustainable Energy for All energy consumption tier system, discussed later in the methodology.
Challenges
Community members may over-estimate their usage resulting in the system being oversized. This is noted to be a common problem in the energy-for-development field. A method of addressing this issue is to ask for a deposit based upon the "customer's" estimated usage.
Times of lighting: Calculation can be based upon solar path and incorporating horizon shading.
Similar to the electrical energy system design, a range of thermal energy systems are produced at this stage by matching demand with supply. First, demand must be quantified as per the results of the Project Definition and Data Collection stages. Potential supply of available fuels with technologies can then be considered to meet this demand. The optimal thermal system from the range produced at this stage is then determined in the following stage Sustainability Analysis.
The thermal needs of the community will determine the end use of the thermal energy. The following steps should be undertaken to determine the thermal energy system design options:
A) Simple improvements of existing technologies
B) Replacement of technology
Current community statistics would be required to determine the current demand and to establish a range of thermal energy system design options. This includes the number of households, number of people per household and the times at which the community use these technologies. In order to determine more specific information a market assessment including a questionnaire on current thermal energy use should be carried out to help determine a more accurate demand profile for the community. This should ideally be done at the start of the Data Collection stage in order to get more reliable information from the beginning of the project. As mentioned above, depending on the community, special adjustments or modifications to the thermal energy system design options may be required. Considerations of adjustments to the design of the thermal technology options proposed would be community specific and could include the following: high temperatures of location, low temperatures, altitude of community or surroundings of the community.
The thermal demand may be easier to determine if there is already thermal energy being used, however challenges may still exist in determining the specific current use. If information is not available through the community on current thermal use then data can be gathered through reviewing literature on methods and technologies currently used. A challenge which may be found for an off-grid developing community where space heating is a priority, is that if space heating is currently met through the use of an open fire used for cooking. This makes it more difficult to determine demand as it is not identified by the community as space heating. Again this would require hand calculations using information found from literature.
A range of technically viable fabric improvements can now be produced to meet the thermal development goal. Like the previous designs above, demand must first be quantified as per the Project Definition stage. This demand is then tested against different insulation materials (“technologies”) using building simulation software to determine the supply required by buildings of different materials. This can be performed using the following steps:
Alternatives to modelling: Modelling can be a time consuming process and still contain a large margin of uncertainty. Tools which take alternative approaches may be suited to the step such as HEM software.
Thermal comfort: This factor is difficult to determine due to the fluid concept of comfort. Some studies in Nepalese mountain communities show "high satisfaction" with indoor temperatures of 10.7°C which is significantly below UK temperatures. This is thought to be due to cultural adaptions such as clothing choice and expectations.
Estimating impact: In many developing communities it is common practice to provide heat through biomass. Biomass is largely free therefore determining the impact of fabric improvements in terms of cost can be misleading. Reducing space heating demand is to reduce time spent gathering and preparing biomass, improve indoor air quality, and increase indoor temperatures. These metrics may be more appropriate but harder to estimate measures of impact.
Availability of materials: Material costs will vary greatly depending upon national availability and transport costs. Alternative materials may be more viable such as compacted earth or straw-bales. There may also exist the potential to recycle wasted products, such as paper and plastic, to create insulating materials and even generate industry. Consideration to building standards (for example fire resistance) should be considered during design.
Vernacular architecture: Building stock may be highly vernacular, especially so in developing communities. A main driver behind why a community is not developed may be due to the specific bioclimatic or geographic conditions, therefore the vernacular building design may reflect this so making accurate modelling difficult.
Modelling: Models may be significantly inaccurate as highlighted by the above. Additionally, there will likely be significant inaccuracies in modelling occupancy, air changes, ventilation, heat delivery, and many other factors. It may be more appropriate to calculate demand reduction in terms of scale rather than energy.
Cultural: There may be no understanding of the benefits of insulation or an entirely neutral general perception. Workshops may be required to counter this.
As energy system design is an iterative process, the different system options which result from electrical thermal matching are put through the final stage of our methodology. The final stage is the ‘Sustainability analysis’ which allows the options to be reviewed against social, economic and environmental parameters to allow us to come to a final system.
To see the energy system design carried out for the case study in Pangboche click here
The next step of the methodology is the Sustainability Analysis