Fourth Power
Fourth Power is a grid-scale thermal energy storage company building a "thermal battery" that stores electricity as heat. Surplus wind and solar power is used to heat blocks of graphite to roughly 2,400 degrees Celsius; molten tin, circulated by an all-ceramic pump, moves that heat in and out of storage, and thermophotovoltaic (TPV) cells convert the stored heat back into electricity when the grid needs it. The company positions the system as a cheaper, longer-duration alternative to lithium-ion for firming a clean grid, and operates a megawatt-scale demonstration facility near Boston. Fourth Power raised a Series A led by DCVC in 2023. This is a company profile in the API Evangelist network; Fourth Power is a hardware and energy company and does not publish a public developer API.
Index entry only — little beyond a description and a link, and nothing machine-readable enough for an agent to act on without a human reading the site first.
API Evangelist profiles Fourth Power the way a machine reads it — 1 machine-readable artifact, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Fourth Power scores 6.8/100 (minimal), with a separate agent-readiness read of 0/100 (human only). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.
Kin Score
How this is scored →scored 2026-07-27 · rubric v0.5
How we profile Fourth Power
Each block below is one kind of artifact we hold for Fourth Power. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
Security Posture 1
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Resources
Every other property we hold for Fourth Power — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Access & Security 1
Authentication, authorization, and security posture
Company 1
The organization behind the API
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