There has been much debate about how areas experiencing renewable explosive growth can manage the myriad of intermittent sources of electricity. But these are mainly focused on regions with mature power grids and relatively static growth in demand. What if you tried to grow renewable energy at the same time that you tried to grow a grid?
A team of researchers from the EU and the US. USA He decided to find out what a good renewable policy might look like in West Africa, an area similar in size to the 48 contiguous US states. USA But made up of 16 different countries. Some of these nations already get a sizable chunk of their power from renewables in the form of hydropower, but demand is expected to more than double in the next decade or so. Although renewables like solar and wind are likely to play a role based solely on their price, the researchers' analysis suggests that a smart, international grid can balance hydro, wind, and solar to produce a much greener grid. .
Hydro like a giant battery
The new job has a mix of approaches. It runs in the context of the expectation that West African electricity demand will explode in the next decade. Right now, the region has nearly 400 million residents consuming just over 100 terawatt-hours a year (compared to 4,000TW-hr in the United States). By 2030, that demand is expected to exceed 200TW-h, a four-fold increase from demand in 2015.
At the moment, large hydroelectric facilities in West Africa produce around 20 percent of the region's electricity. The rest is mainly supplied by a combination of natural gas and oil generating plants. The additional hydropower plants are in various stages of planning and construction, and the first large solar installations have been opened there in recent years.
However, beyond the growing demand, researchers are interested in discovering how to make the most of the renewable resources available in West Africa. To do this, they analyze how well planned and existing hydropower can serve as a battery-like resource for the addition of intermittent renewable energy such as wind and solar. This requires balancing a combination of retaining a sufficient amount of water behind the dams to keep them running, as well as allowing sufficient flow from the dam to keep the river basin viable. However, within these limits, the dam can contain a sufficient quantity of water and use it to compensate for any deficiencies in the production of other renewable energies.
Time to model
To understand the potential here, the researchers created a computer model that incorporated data on the basic statistics of each dam (or planned dam): incoming flow and precipitation, evaporation of the reservoir, minimum outgoing flow required, and the minimum amount of water that must retain prey, each updated hourly for an entire year using past data. They then used this to calculate an hourly measure of limits on the dam's electricity generation: how much more could it expect to generate if renewables fall short?
With that in hand, the researchers combined this capability with various potential wind and solar projects in a variety of settings. These included a basic case of simply expanding the renewable deployment to match the hydropower's ability to support it; one where the effects of climate change on precipitation were considered; one where wind and solar facilities were strategically oversized to boost production when conditions were mediocre; and one where different nations linked and managed their networks to maximize renewable production.
Well for now, not with growth
The good news is that, at least for the foreseeable future, climate change poses no problem for a hydro-focused plan like this. There are some changes in rainfall over the next decade, but they are minor and largely due to drier regions becoming drier. Since hydroelectric plants do not tend to be located in dry areas to begin with, this has very limited impact.
Another conclusion is that "excess supply,quot; —building more renewable capacity than is technically necessary — can be highly effective. This approach ensures that, at times of maximum productivity, renewable production will exceed demand and should be limited. But, in the researchers' model, an overproduction of 25-30 percent avoided the use of hydroelectric power that could be deployed at times when it was most urgently needed. The net result is that this scenario increased overall use of renewable energy by 20 percent. In other words, although a certain amount of renewable generation was wasted, the overall loss at the system level was quite small.
And, in general, the system is effective. Even in the baseline scenario, the researchers estimate that it could provide almost half of the region's current energy demands in a good year. Increased solar generation could increase that figure by 20 percent. And adding connections and management to the cross-border network could maximize production on approximately 70 percent of the region's current needs.
The downside is that, in just a decade, that 70 percent figure is expected to drop to about 32 percent. That being said, parts of North West Africa border the Sahara and have the potential for a massive increase in solar productivity, and the authors did not consider the potential of the pumped hydro, which can reverse the flow of water in dams for potential store generator for later. The combination of excess solar production and sets of dams acting as a giant battery could substantially increase the productivity of renewable energy.
Sharing is showing interest
In any case, the report makes it clear that not only rich and industrialized countries can benefit from the continuing drop in the price of renewable energy. Even with the added costs of overproduction, the authors estimate that the system could work at a price that is about 10 percent cheaper than expanding the cost of natural gas.
However, one of the challenges will be balancing the political needs and expectations of 16 different countries. Right now, those with access to good water resources are planning to meet their climate commitments by using them. Without a doubt, it will take a lot of work to get them to agree to export part of that energy in exchange for receiving renewable energy generated by facilities in another country that have not yet been built.
Nature Sustainability, 2020. DOI: 10.1038 / s41893-020-0539-0 (About DOIs).