"Delivering" isn't really a thing. The value of solarcoin like all currencies is derived from 2 economic utility functions (transactional & speculative). Ignoring speculative which is volatile, it is about network size.  (see video on on site).  Most currencies representing a belief in value (USD, EUR, Gold, BTC) have a network node (potential acceptor of the currency)/total circulating value of $1,000-$2,000. Roughly speaking the transactional utility of solarcoin is estimated at around $1 with 50,000 user / claimants.  There are 7m solar producers globally growing at 20-40% annually. I am working on the white paper explaining this.