As a leading renewable energy, prospects PV power is still overshadowed by three major problems:
Problem 1: PV cell cost
Dr. Varun Sivaram, an expert at an nonprofit think tank, notes that for PV power to attain 30% share on the global power market, its price must plunge to 25 cents/watt, one quarter of existing US$1.
Sivaram believes that the key to cutting PV power cost is to commercialize perovskite cell, whose price and process temperature is much lower than existing mainstream silicon cell. Much progress has made in the development of perovskite cell, whose optical conversion rate has hit 25%, from mere 3.8% at the start.
Meanwhile, perovskite cell can be made in the form of flexible color film for extensive applications, such as PV-cell color-changeable window, which has been developed by a U.S. research team.
For its commercialization, perovskite cell, however, has to overcome the problem of instability, as perovskite crystal tends to dissolve in humidity. Another problem is that with existing perovskite cell resembling only a nail in size, scientists have yet to develop large-sized perovksite cell with comparable high efficiency.
Sivaram laments that despite its rosy outlook, investments by the energy industry in perovskite cell is still grossly insufficient, which will block its early commercialization. R&D expense typically accounts for 1-2% of energy companies' profits, only one tenth that of semiconductor companies. The U.S. federal government's budget for R&D on renewable energy reaches only US$5 billion a year now, which will be overtaken by that of Chinese government by 2020.
Problem 2: Power management
Supply of PV power is sporadic, with output often peaking at a time of low demand, and vice versa. Output also often has to be distributed to other countries, due to insufficient grid capacity, such as California which often provide excess output of its PV power network, for 10% share of its power need, to other states.
Given high PV cell cost, large-scale energy storage system is unfeasible for now. Data of U.S. Department of Energy shows that PV cells accounts for only 1.7% of U.S. grid's power storage, with the rest all being stored in the form of pumped-storage power stations.
Ramez Naam, instructor for energy environment at Singularity University and a angel-fund investor, points out that the most direct solution to the problem is the installation of bigger and more distributed grid. The most ideal state for the U.S. is to connect the three major grids, covering eastern region, western region, and Texas, respectively, with new high-voltage power boxes, which, though, may cause confusion in power management.
Problem 3: high indirect cost
On top of technological problem, indirect cost for the installation of PV power plants is also very high, including design of the project, approval of the project, site selection, and grid connection, which could account for 64% of the total cost, leaving the remainder to PV cell and hardware, according to the U.S. Department of Energy.
Cost for rooftop PC panel and cell is also too high to be accepted by most people now, who may still hope to have grid as backup for power supply, even if they have rooftop PV power system on the roofs of their houses.
(First photo courtesy of Jon Callas via Flickr CC BY 2.0)