Project Persephone

Small hydro - small scale hydroelectric power generation

Project Persephone's aid and development agenda focuses on equatorial mountain regions, for their potential to reduce space launch costs through projectile space launch. Although projectile space launch should be relatively modest in its energy requirements, it will nevertheless require a significant amount of energy. Local, renewable sources, with low environmental impact, should naturally be preferred. Small hydro holds great promise as a candidate technology.

Hydroelectric is not without its problems. Large-scale hydroelectric dams in the developing world have been:

• an economic boondoggle in far too many cases,¹
• very often a disaster, environmentally,² and
• sometimes profoundly disruptive, culturally³

However, small hydro appears to be nearly ideal in these respects:

• excellent yield of value for the (often very low) investment in relatively simple technology^{4 5 6}
• renewable with relatively low regional impact
• amenable to local development and control
• methane emissions may be offset in situ, with extraction of emissions from the reservoir for use as a local fuel.⁷. This approach does not look economical at today's prices for natural gas, but if prices go up (and especially with carbon taxation/trading), it may become more so, and especially if floating solar can help trap methane before it's released by ebullition.⁸ Research on methane extraction continues.⁹

Perhaps best of all, the scale of many small hydro projects means that a community might be able to do much of the construction work itself, if provided with a few of the more expensive components.

Mountain regions provide both watersheds and altitude, the main siting requirements. Some equatorial regions enjoy a great deal of rainfall (even some snow), which provides the essential ingredient. Communities in these regions are typically impoverished, and suffering from "benign neglect" by their often-unusually-corrupt national governments. Small hydro development in such communities could bring in jobs for skilled labor, whetting local appetites for education, and for quality of life improvements. The electricity could become an export product for the community. And the community could also enjoy some added labor productivity at reduced energy cost wherever water turbines can be use for direct drive of tools.¹⁰,¹¹ A sawmill and woodshop for wood-product factory production could be incorporated into the dam structure itself, which would help amortize the investment in dam construction.

Small hydro should also provide these communities with added incentives to manage their watersheds, particularly through sustainable forestry: precipitation from cloud forests as a "buffer", by smoothing out the annual flows in the watershed, improves the availability of water while reducing spillway waste during peak rains and thaws.

Dormant and extinct stratovolcanoes - which are common near the equator - often feature caldera lakes. A straight channel bored upslope -- even a rather narrow one¹² -- could draw sustainably from such caldera lakes, initially generating electricity through a series of water turbines. This same channel could eventually be considered a "pilot channel" for a series of projects eventually leading to a steep tunnel that houses a projectile launch tube. Such channels could be established with tunnel boring machines? -- some of these can drill very straight tunnels as narrow as one meter wide.

¹ Hydropower externalities: A meta-analysis, M Mattmann, et al., https://www.sciencedirect.com/science/article/pii/S0140988316300950 ⇑

² Including at the level of GHG emissions beyond the methane emissions in the reservoir itself, see e.g., A natural experiment reveals the impact of hydroelectric dams on the estuaries of tropical rivers, E Ezcurra et al., https://advances.sciencemag.org/content/5/3/eaau9875 ⇑

³ The Dam Building Boom: Right Path to Clean Energy?, David Biello, http://e360.yale.edu/content/feature.msp?id=2119 ⇑

⁴ Bario Asal & Arur Layun Micro-Hydro Project http://kelabit.net/bariohydro/index.htm ⇑

⁵ Pico Hydro Power, Intermediate Technology Development Group, Kenya http://www.t4cd.org/Resources/ICT_Resources/Projects/Pages/ICTProject_287.aspx ⇑

⁶ Hydropower remains the lowest-cost source of electricity globally https://www.hydroreview.com/business-finance/hydropower-remains-the-lowest-cost-source-of-electricity-globally/#gref ⇑

⁷ Methane stocks in tropical hydropower reservoirs as a potential energy source, FM Ramos et al., https://link.springer.com/article/10.1007%2Fs10584-008-9542-6 ⇑

⁸ https://en.wikipedia.org/wiki/Floating_solar ⇑

⁹ https://www.bbc.com/future/article/20240326-how-hydroelectric-dams-are-a-hidden-source-of-carbon-emissions ⇑

¹⁰ See e.g. http://www.microhydropower.net/basics/drive.php ⇑

¹¹ Transmission losses can average 6%, and for remote regions, higher. See e.g., http://insideenergy.org/2015/11/06/lost-in-transmission-how-much-electricity-disappears-between-a-power-plant-and-your-plug/ ⇑

¹² Tunnel boring machines can be as narrow as one meter wide, and have already been used in hydropower projects; see, e..g, https://me.smenet.org/abstract.cfm?preview=1&articleID=9661&page=138 ⇑