Spurred by substantial subsidies, renewable energies have reduced their costs and captured a steadily growing market share. However, the variability of solar and wind power leads to new challenges for power systems. Policy instruments for steering the energy transition towards a zero-carbon future must account for this. We consider an economy in which competitive firms use pollutive fossils, intermittent renewables, and storage for electricity production. A Pigouvian tax is still efficient, because price fluctuations that result from intermittent renewables provide sufficient incentives to invest in storage capacities. However, governments have proved reluctant to impose carbon taxes. Therefore, we examine second-best subsidies when carbon pricing is imperfect. The optimal subsidy rate for renewables decreases as electricity production becomes less reliant on fossils. The storage subsidy is usually negative as long as fossils are dispatched while filling the storage, but turns positive thereafter. This is because more storage capacity reduces the price when stored electricity is supplied to the market, but raises it when storage adds to demand. This has countervailing effects on firms’ incentives to invest in fossil capacities. A numerical simulation illustrates that substantial subsidy payments are required even after fossils have been completely driven out of the market.

在大量补贴的刺激下，可再生能源降低了成本并获得了稳步增长的市场份额。然而，太阳能和风能的可变性给电力系统带来了新的挑战。引导能源转型走向零碳未来的政策工具必须考虑到这一点。我们考虑这样一种经济，其中竞争性公司使用污染性化石、间歇性可再生能源和电力生产储存。庇古税仍然有效，因为间歇性可再生能源导致的价格波动为投资存储容量提供了足够的激励。然而，事实证明，政府不愿意征收碳税。因此，当碳定价不完善时，我们研究次优补贴。随着电力生产对化石的依赖减少，可再生能源的最佳补贴率下降。只要化石在填满仓库时发出，储存补贴通常是负数，但此后变为正数。这是因为当存储的电力供应给市场时，更多的存储容量会降低价格，但当存储增加需求时会提高价格。这对企业投资化石产能的动机产生了抵消作用。数值模拟表明，即使化石已完全退出市场，仍需要支付大量补贴。这是因为当存储的电力供应给市场时，更多的存储容量会降低价格，但当存储增加需求时会提高价格。这对企业投资化石产能的动机产生了抵消作用。数值模拟表明，即使化石已完全退出市场，仍需要支付大量补贴。这是因为当存储的电力供应给市场时，更多的存储容量会降低价格，但当存储增加需求时会提高价格。这对企业投资化石产能的动机产生了抵消作用。数值模拟表明，即使化石已完全退出市场，仍需要支付大量补贴。