NEST
The NExus Solutions Tool (NEST) is an open modelling platform that integrates multi-scale energy–water–land resource optimization with distributed hydrological modelling. The approach provides insights into the vulnerability of water, energy and land resources to future socioeconomic and climatic change and how multi-sectoral policies, technological solutions and investments can improve the resilience and sustainability of transformation pathways while avoiding counterproductive interactions among sectors. NEST can be applied at different spatial and temporal resolutions, and is designed specifically to tap into the growing body of open-access geospatial data available through national inventories and the Earth system modelling community.
The documentation and code for the initial case studies is published by Vinca et al., 2020. For this application, a newer version of NEST has been developed, which uses the MESSAGEix framework developed at IIASA and allows the generation of country models with representation of the Energy-water-land systems similar to the previously developed NEST model in Vinca et al., 2020. This new version has been published as the open-source module MESSAGEix-Nexus (links to Code and Documentation), therefore the names NEST and MESSAGEix-Nexus might be used interchangeably in this documentation.
Temporal and spatial resolution The time horizon and the temporal and spatial resolution of NEST can be defined by the user, assuming that data is available to populate the required parameters. For the LEAP-RE application on Zambia, the model has 10-year time steps starting from 2020 until 2060 and monthly sub-annual timesteps. Spatially, some sector are defined at the country level and other at the Basin Country Units (BCU) wich are defined by crossing HYDROSHED basins (level 4) with Zambian administrative boundaries.
| Sector | Temporal resolution | Spatial resolution |
|---|---|---|
| Electricity supply connected to the grid | yearly | country |
| Primary energy resources | yearly | country |
| non-electricity energy demands | yearly | country |
| off-grid electricity demand and supply | monthly | BCU |
| Water balance and infrastructure | monthly | BCU |
| Irrigation requirements from crops | monthly | BCU |
To understand the Energy system of a MESSAGEix model we recommend looking at the comprehensive documentation of MESSAGEix-GLOBIOM.
The detailed description of the updated MESSAGEix-Nexus module is currently under review and will be made available soon.
The land sector is in this country-model version simplified to only consider agriculture and irrigation. Crop land use, yield and water withdrawals are estimated from WaterCrop and used as input in NEST.
The documentation of the code needed to compile and run NEST is available and regularly updated at the MESSAGEix documentation