Green heating:Theory and practice

Energy conservation in heating systems has great influence on overall sustainable development strategy. Heating technology, especially combined heat and power(CHP, cogeneration), has been attracting increased interest and rapidly developing in recent years. However, the theoretical potential of heating from the perspective of thermodynamics has not been clearly illustrated. This paper presents a theoretical analysis of heating systems based on the 1st and 2nd laws of thermodynamics using the specific fuel consumption(SFC) analysis method, clarifies the theoretical potential limitation of heating systems and illustrates the process of reversible heating on the basis of the total energy system. A novel concept(green heating, GH) and a new indicator(green-heating index, GH Index) are scientifically defined to characterise different options for heating and to quantitatively evaluate their fuel consumption levels. Thereafter, the fuel consumptions of four typical space heating modes are compared and discussed to present the application of GH theory and validate the power of the proposed concept and index. Furthermore, two different CHP technologies are analyzed with an instantiation case, and a novel CHP system is recommended, which may scientifically support the development of heating technology and further improve the processes of energy-saving and CO2 reduction.

Orbital electronic heat capacity of hydrogenated monolayer and bilayer graphene

The tight-binding Harrison model and Green＇s function approach have been utilized in order to investigate the contribution of hybridized orbitals in the electronic density of states（DOS） and electronic heat capacity（EHC） for four hydrogenated structures, including monolayer chair-like, table-like, bilayer AA- and finally AB-stacked graphene. After hydrogenation, monolayer graphene and bilayer graphene are behave as semiconducting systems owning a wide direct band gap and this means that all orbitals have several states around the Fermi level. The energy gap in DOS and Schottky anomaly in EHC curves of these structures are compared together illustrating the maximum and minimum band gaps are appear for monolayer chair-like and bilayer AA-stacked graphane, respectively. In spite of these, our findings show that the maximum and minimum values of Schottky anomaly appear for hydrogenated bilayer AA-stacked and monolayer table-like configurations, respectively.

Controlling Thermodynamic Properties of Ferromagnetic Group-Ⅳ Graphene-Like Nanosheets by Dilute Charged Impurity

Using the Kane-Mele Hamiltonian, Dirac theory and self-consistent Born approximation, we investigate the effect of dilute charged impurity on the electronic heat capacity and magnetic susceptibility of two-dimensional ferromagnetic honeycomb structure of group-Ⅳ elements including silicene, germanene and stanene within the Green's function approach. We also find these quantities in the presence of applied external electric field. Our results show that the silicene(stanene) has the maximum(minimum) heat capacity and magnetic susceptibility at uniform electric fields. From the behavior of theses quantities, the band gap has been changed with impurity concentration, impurity scattering strength and electric field. The analysis on the impurity-dependent magnetic susceptibility curves shows a phase transition from ferromagnetic to paramagnetic and antiferromagnetic phases. Interestingly, electronic heat capacity increases(decreases) with impurity concentration in silicene(germanene and stanene) structure.