| The problems of high energy consumption,low energy efficiency,unreasonable planning,low construction standards and short life span of traditional buildings in China are the main reasons for the high carbon emissions of the construction industry.In the face of such a large scale of urban and rural traditional building holdings,transforming them into green buildings compared to demolition and reconstruction can not only improve the utilization of building energy and resources,but also reduce the growth of carbon emissions from steel,cement and other building materials industries and reduce environmental pollution,which is an important way to reduce emissions in China’s construction industry at present.In order to promote the smooth development of green renovation work,in view of the existing problems of difficult financing and poor operation effect of green renovation,this paper starts from the perspective of government subsidy mechanism design,introduces green renovation PPP model,considers carbon trading mechanism and two-stage subsidy mechanism,and discusses how to improve the subsidy of green renovation PPP project around two aspects of exploring the optimal two-stage subsidy plan and the evolution law of two-stage subsidy mechanism The mechanism of green retrofitting PPP projects will be improved and the operation effect of green retrofitting projects will be improved.Firstly,we construct a three-party Stackelberg game model for green retrofit PPP projects with government,social capital and consumers,and compare and analyse the project energy savings and two-phase effort level of social capital side under three different subsidy mechanisms,namely no government subsidy,single-phase subsidy and two-phase subsidy,to explore the incentive effect of subsidy on the retrofit quality of social capital.And to explore the optimal subsidy scheme under the government’s two-phase subsidy for social capital and consumers based on retrofit quality and operational effectiveness.The results show that:(1)the change from a single-phase subsidy mechanism to a two-phase subsidy mechanism is a Pareto improvement,with both the project energy savings and the two-phase effort level of social capital being increased;(2)the incentive intensity of energy savings under the two-phase subsidy decreases with the increase of the two-phase effort cost coefficient of the social capital side,and the optimal incentive intensity decreases with the increase of the effort impact factor between the two phases;(3)the optimal incentive intensity increases with the increase of the two-phase effort complementary effect and decreases with the increase of the marginal cost of public finance funds;(4)there is a substitution effect between carbon price and incentive intensity,and the increase of carbon price can motivate social capital to increase the two-phase effort level.The results of the study can provide reference for the government to design a subsidy mechanism for green retrofit projects.Secondly,a tripartite evolutionary game model was constructed to discuss how the subsidy mechanism and related variables affect the optimal evolutionary stability of the tripartite game system under the two-stage subsidy mechanism implemented by the government.The results show that:(1)the strategy selection process of the government,social capital and consumers is influenced by the parameters of energy saving incentive coefficient,operational energy saving standard,carbon price,carbon trading invisible benefit coefficient and carbon quota;(2)the higher the energy saving incentive coefficient and the lower the operational energy saving standard,the more the social capital and consumers receive the second stage subsidy,and the more social capital and consumers tend to(3)the increase of carbon price,carbon quota and invisible benefit coefficient of carbon trading can effectively promote the evolution of the three parties to the ideal equilibrium state of "government incentive,social capital investment,and consumer participation". |
