Moss

The Caverns of Agano

The city of Agano is in a secret underground location to protect its people from enemies. One of the main problems was how to find adequate fuel and power sources.
Fortunately for the citizens of this place, Agano is also known as the 'science city' and there is an abundance of great minds naturally adept at problem-solving. When searching for a location for their city, one of the fundamental criteria the founders had was for it to be near to a fuel source, or be capable of producing its own. In the final analysis, they chose a location that had both. 

Inspiration from the Ocean

One of the founder members was from an aquatic race - his real name, and that of his race is unpronounceable to all humanoids. He was named by the founder whom he first met, and in his language, the word for water is nero.
Nero spoke of how his people used floating platforms laced with growing algae that when absorbing light produced energy as a byproduct. They collected this and ran it down to their settlement locations on the ocean bed.
A similar method was possible in the caverns chosen to house Agano. In this particular location, there are vast areas covered in a moss that appeared to have a phosphorescent quality. The scientists constructed huge panels, molded to match the terrain above them, with the moss grown on top and placed them on the surface. Here the moss could get energy from the sun (and far more than in the caverns) to fuel its growth. 
Scientists explained that tiny organisms in the soil break down compounds produced by the moss during its growth. Using a combination of technology and magic, they constructed 'cables' and storage tanks that could harness and store the byproduct of this process, an energy they called Denki. 
The energy produced appears to be much higher than normal because of a higher concentration of magical energy in the atmosphere here. They are unsure as to why it is higher but for now, it serves them well.

Other Uses

The city is located in caverns situated beneath mountains in the northern part of Acaria.
The moss they found here has phosphorescent properties, which they use as ambient lighting during the night time when little sunlight permeates through the rock channels they have bored above them.
The moss also burns well as it has a high oil concentration. Scientists also believe they may be able to convert this oil into a burning fuel but are still working on ways in which to achieve that.

Capacity & Other Sources

With denki energy, they can power generators to supply light and heat to about 20% of the city. 
Although not enough on its own, there are many other projects such as this in operation across the city, cavern system, and surface, harnessing the natural sources of energy all around them - sunlight, wind from the surface, and underground river systems.

Cover art by: Mysticartdesign https://pixabay.com/users/mysticsartdesign-322497/